981 0516 Onan 10KW HDKAG Genset Service Manual (10 1997) W 1051 Supl

User Manual: 981-0516 Onan 10KW HDKAG Genset Service manual (10-1997) w-981-1051 Supl

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Service Manual
10.0 kW HDKAG Generator Sets

Printed in U.S.A.

981-0516
10-97

Supplement 981Ć1051
Date: 02Ć05
Insert withĆ
Title: HDKAG Service Manual
Number (Date): 981Ć0516 (10Ć97)

This Supplement transmits changes to Figure 4-5 to illustrate the location of the voltage adjustment pot on
newer voltage regulator boards. Replace Sheet 4-5/4-6 with the attached sheet.

Page 1 of 1
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by any means, is strictly prohibited.

GENERATOR OPERATION

which in turn supplies the field. Rated output
voltage is thereby maintained as the load varies.

Refer to Figures 4-3 and 4-4, the generator schematics, while working through the following description.

ELECTRONIC VOLTAGE REGULATOR

1. Voltage regulator VR1 (three-phase: VR21)
supplies DC to the field winding (F1 - F2 leads)
through brushes and slip rings, thereby establishing a revolving 4-pole magnetic field. The
battery is connected during startup to initiate
field excitation. Voltage regulator VR1 supplies
field current during operation. Rated output
voltage is maintained as the generator load
varies, by varying field current to maintain field
strength proportional to the load.
2. The revolving magnetic field induces AC in the
stator windings (T1 - T2 and T3 - T4) which are
connected to the load.
3. Under light load, the stator windings can supply
sufficient current for the field to maintain rated
output voltage.
4. As the load increases, load currents increase,
resulting in a proportional increase of current,

The voltage regulator controls the output of the generator so that a constant voltage is maintained under varying load conditions.
Only the basic functions of the regulator are described (Figure 4-5). Voltage from quadrature windings Q1/Q2 supply power to the voltage regulator itself. The voltage regulator in turn supplies an excitation voltage (F1/F2) that is directly proportionate
to the output voltage (L1/L0) it senses. Any
changes in the generator output voltage produce a
corresponding change in the excitation voltage provided by the regulator.
On the HDKAG, the voltage regulator assembly includes a potentiometer which enables a slight degree of output voltage adjustment. The voltage regulator assembly contains no user-serviceable
parts. If the assembly fails, it must be replaced.
NEWER BOARDS

CAUTION: The V/Hz Break Point Pot is
Factory Set and Sealed. DO NOT ADJUST.

OLDER BOARDS

VOLTAGE ADJUST: Trim pot adjusts
output voltage level. Turn pot clockwise to
increase voltage. Turn pot counterclockwise
to decrease voltage.
FIGURE 4-5. ADJUSTMENTS ON GENSET VOLTAGE REGULATOR BOARD

4-5
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GENERATOR SERVICE

4. Install the new brushes and springs in the holder and keep them in place during assembly by
inserting a piece of wire through the holder, as
shown in Figure 4-7.

Always disconnect the battery cables (negative [-]
first) from the battery to prevent accidental starting
of the set while servicing the generator.

5. Install the brush holder. After tightening the
mounting screws, pull out the brush retaining
wire.

WARNING

Accidental starting of the set while
working on it can cause severe injury. To prevent accidental starting, disconnect the battery
cables (negative [-] first) from the battery.

6. Connect the F1 lead to the inner brush terminal
(nearest the rotor windings). Connect the F2
lead to the outer brush terminal (nearest the
end bell).

The negative (-) cable is always disconnected
first, and connected last, to prevent arcing if a
tool accidentally touches the frame or other
grounded metal parts of the set while disconnecting or connecting the positive (+) cable.
Arcing can ignite the explosive hydrogen gas
given off by the battery, and cause severe injury.

Slip Ring Inspection/Replacement
Inspect the slip rings for grooves, pits or other damage. If dust has accumulated on any generator
components, they can be cleaned with filtered lowpressure air.
1. Examine the slip rings while servicing the
brushes.

Brush Inspection/Replacement
The generator should be inspected for brush wear
and cleaning every six months.

2. If the rings need cleaning or service, remove
the rotor from the generator and dress the rings
on a lathe.

WARNING Accidental starting of the generator
set can cause severe personal injury or death.
Stop the generator set and disable by disconnecting the starting battery cables (negative [-]
cable first) before inspecting the generator.

CAUTION Dressing the slip rings on a lathe
improperly may damage the generator rotor.
Make certain that only an experienced technician performs this job.

1. Remove the access cover for the brush assembly.
2. Check the brushes for wear with a piece of wire
marked off 1 inch (25 mm) from one end (Figure 4-6). Replace the brush and the spring if
the wire goes into the brush holder 1 inch or
more.
3. To replace brushes, remove the brush holder
by disconnecting the two leads to the holder
and removing the two mounting screws.

Generator Bearing
Inspect the bearing for evidence of outer case rotation every 1000 hours of use. The bearing should
be replaced every five years, because the bearing
grease gradually deteriorates due to oxidation.
Replace the O-ring if it shows evidence of wear or
deterioration. Renew grease if necessary (moly
only).

4-6
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California
Proposition 65 Warning
Diesel engine exhaust and some of its constituents are known
to the State of California to cause cancer, birth defects, and
other reproductive harm.

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by any means, is strictly prohibited.

Table of Contents
SAFETY PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
1

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
About This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Set Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1
1-1
1-1
1-1
1-1
1-3

2

ENGINE CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Start Control at Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2-1
2-1
2-1
2-6

3

ENGINE CONTROL SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[A] Battery Check (BT1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[B] Battery Cable Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[C] Battery Charging Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[D] Start Solenoid Check (K11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[E] Heater (Glow Plug) Relay Check (K13) . . . . . . . . . . . . . . . . . . . . . . . . . .
[F] Fuel Solenoid Check (K14) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[G] Start/Stop Switch Check (S11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[H] Power Relay Check (A11-K12) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-1
3-1
3-1
3-1
3-1
3-1
3-2
3-2
3-2
3-2

4

GENERATOR/VOLTAGE REGULATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generator Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electronic Voltage Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generator Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generator Disassembly/Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-1
4-1
4-5
4-5
4-6
4-8

5

GENERATOR/REGULATOR TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . 5-1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
Troubleshooting Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

6

GENERATOR/REGULATOR TESTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[A] Testing Field Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[B] Testing Generator Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[C] Testing Generator Stator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[D] Dynamic Rotor/Stator Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[E] Voltage Regulator Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[F] Wiring Harness Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[G] Voltage Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[H] Reconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6-1
6-1
6-1
6-1
6-2
6-3
6-5
6-5
6-5
6-5

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i

7

ROUTINE MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
Maintenance Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
Generator Set Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2
Oil and Filter Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3
Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4
Fan Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6
Fuel System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
Air Cleaner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9
Battery Care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9
AC Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10
Crankcase Breather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10
Muffler/Spark Arrester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11
Cleaning the Generator Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11
Initial Starting and Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11

8

WIRING DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

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ii

Safety Precautions
Thoroughly read the OPERATOR’S MANUAL
before operating the genset. Safe operation and
top performance can be obtained only with
proper operation and maintenance.

• Used engine oil has been identified by some
state and federal agencies as causing cancer
or reproductive toxicity. Do not ingest, inhale,
or contact used oil or its vapors.

The following symbols in this Manual alert you to
potential hazards to the operator, service person
and equipment.

• Benzene and lead in some gasolines have
been identified by some state and federal
agencies as causing cancer or reproductive
toxicity. Do not to ingest, inhale or contact gasoline or its vapors.

Alerts you to an immediate hazard
which will result in severe personal injury or
death.

• Do not work on the genset when mentally or
physically fatigued or after consuming alcohol
or drugs.

Alerts you to a hazard or unsafe
practice which can result in severe personal injury or death.

• Carefully follow all applicable local, state and
federal codes.

Alerts you to a hazard or unsafe
practice which can result in personal injury or
equipment damage.

GENERATOR VOLTAGE IS DEADLY!
• Generator output connections must be made
by a qualified electrician in accordance with applicable codes.

Electricity, fuel, exhaust, moving parts and batteries
present hazards which can result in severe personal injury or death.

• Make sure all fasteners are secure and torqued
properly.

• The genset must not be connected to the public
utility or any other source of electrical power.
Connection could lead to electrocution of utility
workers, damage to equipment and fire. An approved switching device must be used to prevent interconnections.

• Keep the genset and its compartment clean.
Excess oil and oily rags can catch fire. Dirt and
gear stowed in the compartment can restrict
cooling air.

• Use caution when working on live electrical
equipment. Remove jewelry, make sure clothing and shoes are dry and stand on a dry wooden platform on the ground or floor.

• Let the engine cool down before removing the
coolant pressure cap or opening the coolant
drain. Hot coolant under pressure can spray
out and cause severe burns.

FUEL IS FLAMMABLE AND EXPLOSIVE

GENERAL PRECAUTIONS
• Keep ABC fire extinguishers handy.

• Keep flames, cigarettes, sparks, pilot lights,
electrical arc-producing equipment and
switches and all other sources of ignition well
away from areas where fuel fumes are present
and areas sharing ventilation.

• Before working on the genset, disconnect the
negative (- ) battery cable at the battery to prevent starting.

• Fuel lines must be secured, free of leaks and
separated or shielded from electrical wiring.

• Use caution when making adjustments while
the genset is running—hot, moving or electrically live parts can cause severe personal injury or death.

• Use approved non-conductive flexible fuel
hose for fuel connections at the genset.

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iii

ENGINE EXHAUST IS DEADLY!

BATTERY GAS IS EXPLOSIVE

• Learn the symptoms of carbon monoxide poisoning in this Manual.

• Wear safety glasses and do not smoke while
servicing batteries.

• Never sleep in the vehicle while the genset is
running unless the vehicle has a working carbon monoxide detector.

• When disconnecting or reconnecting battery
cables, always disconnect the negative (- ) battery cable first and reconnect it last to reduce
arcing.

• The exhaust system must be installed in accordance with the genset Installation Manual.
• Do not use engine cooling air to heat the vehicle interior.

DO NOT OPERATE IN FLAMMABLE AND
EXPLOSIVE ENVIRONMENTS

• Make sure there is ample fresh air when operating the genset in a confined area.

Flammable vapor can cause a diesel engine to
overspeed and become difficult to stop, resulting in
possible fire, explosion, severe personal injury and
death. Do not operate a diesel-powered genset
where a flammable vapor environment can be
created by fuel spill, leak, etc., unless the genset is equipped with an automatic safety device
to block the air intake and stop the engine. The
owners and operators of the genset are solely responsible for operating the genset safely. Contact
your authorized Onan/Cummins dealer or distributor for more information.

MOVING PARTS CAN CAUSE SEVERE
PERSONAL INJURY OR DEATH
• Do not wear loose clothing or jewelry near moving parts such as PTO shafts, fans, belts and
pulleys.
• Keep hands away from moving parts.
• Keep guards in place over fans, belts, pulleys,
etc.

Mobile-3

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iv

1. Introduction
ABOUT THIS MANUAL

SAFETY CONSIDERATIONS

This manual contains troubleshooting and repair
data for these components of the HDKAG generator set:

Generator sets present safety hazards that the
technician must know about. Read the precautions
on the inside cover of this manual. Familiarize yourself with the hazards shown in Table 1-1. When the
hazards are known, approach the job with a safetyconscious attitude. Being safety-conscious is the
best way to avoid injury. Reduce the chance of an
accident with the following safeguards.

• Control
• Generator
See the Engine Service Manual for engine information.

Safeguards To Avoid Hazards

Study this manual carefully. Heed all warnings and
cautions. Proper use and maintenance can result in
longer set life, better performance and safer operation.

• Use Protective Clothing. Protect your body
by wearing protective clothing such as:

• Safety shoes
• Gloves
• Safety glasses
• Hard hats

This manual contains basic wiring diagrams and
schematics for troubleshooting.
Technicians
should use the wiring diagram and schematic
shipped with each unit. Update these diagrams and
schematics when the set is modified.

Leave rings and jewelry off. Do not wear loose
clothing that might get caught on equipment.

PC board information is limited; in the field, it is
more efficient to replace the boards than to attempt
repair.

• Reduce Workshop Hazards.
• Keep guards and shields in place on

ASSISTANCE

machinery

• Maintain equipment in good working order
• Store flammable liquids in approved

When contacting an Onan distributor, supply the
complete model number and serial number shown
on the Onan nameplate on the side of the generator
control box.

•
•
•

TEST EQUIPMENT
•
•
•
•
•
•
•
•

Multimeter/digital VOM
AC voltmeter
DC voltmeter
Frequency meter
Jumper leads
Load test panel
Megger or insulation resistance meter
Wheatstone bridge or digital ohmmeter

•

containers away from open flame, spark,
pilot light, cigarette, or other ignition source
Keep the workshop clean and well-lighted
Provide adequate ventilation
Keep a fire extinguisher and safety
equipment nearby
Be prepared to respond to an emergency

• Develop Safe Work Habits.
Unsafe actions are the source of most accidents with tools and machines. Be familiar with
the equipment and know how to use it safely.
Use the right tool for the job, and check its condition before starting. Observe the warnings
and cautions in this manual and take special
precautions when working around electrical
equipment. Do not work alone if possible and
do not take unnecessary risks.

WARNING Incorrect service or replacement of
parts can result in severe personal injury,
death, and /or equipment damage. Service personnel must be qualified to perform electrical
and mechanical service.

1-1

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• Be prepared if an accident occurs.

to be ready to respond to an accident. Learn to be
safety conscious and make safe practices a part of
your work routine. Do not work when tired or after
consuming any alcohol or drug that makes the operation of equipment unsafe.

Agencies such as the Red Cross and local police
and fire departments offer courses in first aid, CPR,
and fire control. Take advantage of this information

TABLE 1-1
HAZARDS AND THEIR SOURCES

• Fire and explosions
• Leaking fuel
• Hydrogen gas from charging battery
• Oily rags improperly stored
• Flammable liquids improperly stored
• Any fire, flame, spark, pilot light, arcproducing equipment or other ignition
sources

• Burns
• Hot exhaust pipes
• Hot engine and generator surfaces
• Hot engine oil
• Electrical short in DC wiring system
• Hot engine coolant
• Poisonous gases
• Carbon monoxide from faulty exhaust
pipes, joints or hangers
• Operating generator set where
exhaust gases can accumulate

• Electrical shock (AC)
• Improper genset load connections
• Faulty RV wiring
• Faulty electrical appliance
• Faulty genset wiring
• Working in damp conditions
• Jewelry touching electrical components
• Rotating Machinery
• Flywheel fan guard not in place
• Jewelry or loose clothing catching in
moving parts

• Slippery Surfaces
• Leaking or spilled oil
• Heavy Objects
• Removing generator set from RV
• Removing heavy components

1-2

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3. Disconnect the remote control plug wire from
the generator set (if applicable).

SET REMOVAL
Some service procedures require removing the
generator set from the vehicle. Because of the wide
variety of installations, it is not possible to specify
exact removal procedures for each genset. If a satisfactory method for removing a particular set cannot be determined, contact the vehicle manufacturer or the set installer for their recommendations.

4. Disconnect the generator load wires. Tag for
identification when reconnecting.
5. Disconnect the exhaust system and support
brackets or hangers, to allow set removal.

WARNING Generator sets are heavy and they
can cause severe personal injury or death if
dropped during removal. Use adequate lifting
devices to provide sufficient support for the set.
Keep hands and feet clear while lifting the generator set. Before starting set removal, place
the transmission in park, set the emergency
brake, and remove the negative (-) cable from
the vehicle ignition system battery to avoid inadvertent movement of the vehicle.

6. Disconnect the fuel line at the genset housing.
Securely plug the end of the fuel line to prevent
fuel leakage.
7. Verify that the set is adequately supported before loosening any mounting bolts or support
members.
WARNING Leakage of fuel presents the hazard
of fire or explosion that can cause severe personal injury or death. Make certain all fuel line
openings are plugged. Before disconnecting
the fuel line, be certain there are no ignition
sources such as flame, spark, pilot light, cigarette, etc., near the generator set. Keep an ABC
type fire extinguisher nearby.

Disconnecting Generator Set Systems
Some installations require partial removal of the set
to gain access to the battery cable, fuel line, and
other connections. Read this entire section before
starting set removal. The following steps are a general guideline.
WARNING Leakage of fuel in or around the
generator set compartment presents the hazard
of fire or explosion that can cause severe personal injury or death. Do not disconnect or connect battery cables if fuel vapors are present.
Ventilate the compartment thoroughly: park vehicles outdoors in a well ventilated area.

When reinstalling the set, be sure all mounting
hardware, and electrical, exhaust, and fuel system
components are connected exactly as they were
before removal. See the appropriate installation
manual during reinstallation for important safety
precautions.

1. Disconnect the generator set negative (-) battery cable at the battery terminal.

Check for oil and fuel leaks. Check the exhaust system audibly and visually with the generator set running. Repair leaks immediately. Replace worn,
damaged, or corroded exhaust and fuel line components before leaks occur.

2. Disconnect the generator set positive (+) battery cable from the wire harness.

1-3

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Blank Page

1-4

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2. Engine Controls
Control Components

GENERAL

The following describes the basic engine control
components and how they function.

This section describes the generator set preheat/
start/run control system. The set may be started either at the onboard DC control box or by using a remotely mounted start control.

A11 Engine Monitor Circuit Board: A circuit board
that monitors the engine control system functions.
This includes starting, stopping, and fault system
operation. Terminals are included for making remote connections. See Figure 2-1.

START CONTROL AT SET
The set is started with a Start/Stop/Preheat switch
on the front panel of the DC control box. Component
references are found on wiring/schematic diagrams
in the Wiring Diagrams section of this manual.

Two relays soldered into the engine monitor board
are not serviceable. They function as follows:
• Power relay K12 connects battery B+ to the

The DC control box does not contain meters and is
designed for remote mounting within limits of the
wire harness (approximately 32 inches [813 mm]).
An optional remote control panel with meters is
available in a kit from Onan.

control meters and fuel solenoid during operation.
• Starter protection relay K15 is AC operated.

When the Start switch is pressed, B+ is connected to K11 start solenoid through the K15
NC contacts until the generator output reaches
about 90 volts AC. At this voltage K15 activates and disconnects the starter circuit.

Switches
Start-Stop/Preheat Switch S11: Starts and stops
the unit locally. Preheat function occurs when the
switch is held in the Stop position. The unit may also
be operated from a remote switch wired to receptacle J3 on the rear panel.

Circuit Breakers

K11 Start Solenoid: Located over the engine monitor circuit board (above K13 glow plug heater solenoid). It connects battery B+ to the start solenoid,
K13 heater solenoid, fuel solenoid and meters during cranking.

DC Control Breaker CB11: A 15 ampere DC
breaker providing protection to the control box wiring and remote wiring from short circuits or overload. Also serves as an emergency stop switch.

K13 Glow Plug Heater Solenoid: Located directly
above the monitor circuit board. Connects B+ to the
engine glow plugs during cranking. It is energized
by K11 start solenoid.

Fault Breaker CB12: A manual reset breaker that
shuts down the engine for low oil pressure and high
coolant temperatures.

K14 Fuel Solenoid: It opens the fuel control valve
when the start/stop switch is placed in the Start
position.

2-1

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by any means, is strictly prohibited.

S11 START-STOPPREHEAT SWITCH

COVER
J3 REMOTE
CONNECTION

J1 AC INPUT

A11 ENGINE MONITOR
CIRCUIT BOARD

RELAY - START
SOLENOID

J2 ENGINE
HARNESS

DC WIRING
HARNESS

CR2 RECTIFIER
ASSEMBLY

DC CONTROL
BREAKER CB11

CB12 FAULT
BREAKER
300-3203

FIGURE 2-1. HDKAG GENERATOR SET DC CONTROL BOX

Engine Monitors

Oil Pressure Monitors
Refer to Figure 2-2 for the location of the oil pressure monitors.

This section briefly describes the engine sensors
(switches) and optional gauge senders. The sensors protect the engine from unfavorable operating
conditions; the senders are used with the operational remote panel. These sealed units are not repairable. Do not use a substitute part if replacement is
necessary, since they are close-tolerance parts
made for a specific application.

Oil Pressure Sender E1: The sender resistance
changes with oil pressure and results in a reading
on the (optional) oil pressure meter. The meter
range is 0 to 100 psi (0 to 700 kPa).
Low Oil Pressure Switch S1: This switch closes if
oil pressure drops to 9 psi (62 kPa), activating the
fault breaker and stopping the engine.
Control Power Latch S6: This oil pressure switch
closes at 5 psi (34 kPa) and provides a latch function for the control circuits. When closed, the switch
supplies a ground path for relay K12 on the engine
monitor board.

The safety sensors (switches) close the fault circuit
to ground if abnormal operating conditions exist,
tripping the fault breaker CB12 to stop the engine.
See Figure 2-2 and the schematic in Figure 2-3.

2-2

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OIL PRESSURE
SWITCH (S1)
(SHUTDOWN)

OIL PRESSURE
SENDER (M12)
COOLANT SHUTDOWN
SWITCH (S2)

OIL PRESSURE
SWITCH (S6)
(POWER LATCH)

COOLANT TEMPERATURE
SENDER (E2)

FIGURE 2-2. HDKAG FAULT SENSOR LOCATIONS

2-3

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Start-Disconnect Sequence: As the generator
gains speed and output voltage, A11-K15 starter
protection relay energizes at about 90 VAC.
A11-K15 NC contact opens and de-energizes start
solenoid relay K11. K11 then disconnects B+ from
the starter solenoid (to stop the cranking motor) and
from the glow plug heaters. If the generator fails to
develop voltage, the engine will attempt to start but
will stop as soon as the Start switch is released.

Engine Temperature Monitors
Refer to Figure 2-2 for the location of the engine
temperature sensors.

Coolant Temperature Sender E2: The resistance
of the sender unit changes with the engine coolant
temperature and causes a reading on the coolant
temperature meter (optional). The meter range is
100° to 250° F (40° to 121° C).

The two K15 NO (normally open) contacts close
and function as follows:

High Coolant Temperature Switch S2: This
switch closes if the coolant temperature rises to
250° F (121° C), activating the fault breaker CB12
and stopping the engine.

• Closes circuit for S1 and S2 (low oil pressure

and high coolant temperature switches respectively)

Control Operation
To understand control operation, refer to the following text and the schematic diagram (Figure 2-3).

• Provides another ground path for K12 coil

Starting Sequence: When start/stop switch S11 is
held in the Stop (preheat) position, battery B+ is
connected to the coil of heater relay K13. The relay
contacts close and connect B+ to heaters HR1 HR4.

Battery Charge Circuit: Alternator G1, powered
by a belt from the engine, supplies B+ voltage to recharge the generator set starting battery through
circuit breaker CB13.

After the preheat time interval, the operator holds
S11 in the Start position. This connects B+ to K14
fuel solenoid relay and through A11-K15 NC (normally closed) contacts to K11 start solenoid relay.
These relays actuate K1 fuel solenoid, B1 solenoid/
starter motor and heaters HR1 - HR4 (via K13 NC
contacts).

Stopping Sequence: Placing S11 in the Stop position puts B+ (through diode CR2) on the ground side
of the A11-K12 power relay. This causes K12 to deenergize and disconnect B+ from CB12 and K1 fuel
solenoid. De-energizing K1 shuts off the fuel flow to
stop the engine.

(through K11 coil) similar to S6.

Fault Shutdown: Fault breaker CB12 opens to
stop the engine any time a fault sensor closes the
circuit to ground. The fault sensors as shown in Figure 2-2 are:

A11-K12 power relay is actuated after a short delay,
when the control power latch switch S6 closes. S6
is closed when oil pressure rises to 5 psi (34 kPa),
assuring engine lubrication before the set reaches
full operating speed. Normally open (NO) contacts
on A11-K12 close, supplying B+ to the other components on the engine monitor board.

• S1 low oil pressure
• S2 high coolant temperature

2-4

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ENGINE PARTS
B1
BT1
E1
E2
HR1-4
E5
K1
S1
S2
S6
G1

Starter and solenoid
Battery (12V)
Sender (oil pressure)
Sender (coolant temperature)
Heater - glow plug
Fuel pump - electric
Fuel solenoid
Switch - low oil pressure
Switch - high coolant
temperature
Switch - control power latch
Alternator

CONTROL BOX PARTS
A11
CB11, 13
CB12
K11

PCB assy - engine monitor
Circuit breaker (control)
Circuit breaker (fault)
Relay - start solenoid
(starter) (12 V)
A11-K12 Relay - power
K13
Relay - heater
K14
Relay - fuel solenoid
A11 - K15 Relay - starter protection
K15
Relay
A11 - R1 Resistor (K12)
A11 - R2 Resistor (LOP timing)
S11
Switch - start/stop/preheat
J3 - J4
Connector - remote

FIGURE 2-3. DC CONTROL SCHEMATIC DIAGRAM

2-5

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Remote Control Operation (Optional): The generator set may be operated from a remote switch
connected to the control receptacle J3. Installation
instructions are furnished with the kit available from
Onan. See Figure 2-4.

J4

CONTROL TROUBLESHOOTING
The information in this section is divided into three
flow charts. Determine the problem and then refer
to the appropriate flow chart (A, B, or C) for the troubleshooting procedures.

J3

A. Engine does not crank.
B. Engine cranks but does not start.
C. Engine starts but stops after running
several seconds.

Before starting a troubleshooting procedure, make
a few simple checks that may expose the problem
and cut down on troubleshooting time.

START-STOP/
PREHEAT

RUN LIGHT

• Check all modifications, repairs, and re-

OIL
PRESSURE

placements performed since last satisfactory operation of set. A loose wire connection overlooked when installing a replacement part could cause problems. An incorrect connection, an opened switch or
circuit breaker, or a loose plug-in are all potential problems that can be eliminated by
a visual check.

WATER
TEMPERATURE

• Unless absolutely sure that panel instruRUNNING TIME
METER

ments are accurate, use portable test meters for troubleshooting.

To troubleshoot a problem, start at the upper-left
corner of chart and answer all questions either YES
or NO. Follow the chart until the problem is found,
performing referenced adjustments or test procedures. Refer to Figures 2-1 through 2-4 for locating
control components, leads, terminals and other
check points.

FIGURE 2-4. REMOTE CONTROL
WIRING DIAGRAM

2-6

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FLOW CHART A. ENGINE DOES NOT CRANK
Many troubleshooting procedures present hazards that can result in severe personal injury or death. Only qualified service personnel with knowledge of fuels, electricity, and machinery
hazards should perform service procedures. Review Safety Precautions.
WARNING

START

Is battery dead?

yes
no

Check CB11 circuit breaker. If okay, jumper
battery cable B+ connection to B1 starter solenoid terminal. Does engine crank?

no

Check battery per Checkout [A] and recharge
or replace. Check battery charger operation
per Checkout [C].

Check battery cables for clean tight connections (ref. Checkout [B]). Check B1 starter solenoid and motor: if bad, repair or replace.

yes

With S11 in Start position, is battery voltage
present between K11 terminal S and ground?

no

yes

If K11 does not energize, test per Checkout
[D] and replace if bad. Is battery voltage present at B1 solenoid terminal with S11 in Start
position?

no

2-7

Check B+ wiring to S11, and between S11 and
K11. Check NC contacts of A11-K15. Replace if bad.
Check B+ wiring between K11 and B1 solenoid terminal. Replace if bad. Check K1
plunger travel for freedom to bottom in solenoid (necessary to open pull coil circuit).

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FLOW CHART B. ENGINE CRANKS BUT DOES NOT START
WARNING Many troubleshooting procedures present hazards that can result in severe personal injury or death. Only qualified service personnel with knowledge of fuels, electricity, and machinery
hazards should perform service procedures. Review Safety Precautions.

START

Is engine getting fuel? Exhaust smoke should
be blue-white and fuel flow steady from fuel
return line.

no

Check fuel system: fuel tank level, shut-off
valves, fuel lines and connections, fuel filters,
fuel pump and injection pump. Okay?
yes

Does K14 fuel solenoid energize when S11 is
in Start position?

yes

no

Is battery B+ applied to glow plug heaters
when switch S11 is in Preheat and Start positions?
yes

Check B+ circuit through S11. Test S11 per
Checkout [G]. Test K14 per Checkout [F].

no

Incorrect fuel? See Operator’s Manual recommendations.

Check switch S11 per Checkout [G]. Check
heater relay per Checkout [E]. Check heater
wiring.

2-8

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FLOW CHART C. ENGINE STARTS BUT STOPS AFTER RUNNING SEVERAL SECONDS
WARNING Many troubleshooting procedures present hazards that can result in severe personal injury or death. Only qualified service personnel with knowledge of fuels, electricity, and machinery
hazards should perform service procedures. Review Safety Precautions.

Is a fault condition indicated by fault breaker
CB12 on control panel?

yes

Check for a possible fault condition. If none,
check fault monitors S1 through S4 and fault
breaker CB12 for improper wiring.

no

Check relay K12 per Checkout [H]. Is K12
good?

no

yes

Does DC control breaker trip after generator
set is started?

yes

2-9

Check for closing of S6 power latch switch. If
switch is OK, check mechanical adjustment of
K1 solenoid: is rod adjusted to correct length
to allow the hold-in coil of K1 to latch? If K1
adjustment is OK and problem remains, replace engine monitor PC board.

Check all B+ wiring for shorts to ground.
Check fuel solenoid adjustment.

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Blank Page

2-10

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3. Engine Control Service
2. From the battery positive post to the battery terminal stud on the solenoid

GENERAL
The following checks are referred to in the Control
Troubleshooting flow charts. They isolate circuit
problems caused by faulty engine control components. Disconnect leads before testing components.

Normally these should be less than 0.3 volts. If extra-long battery cables are used, slightly higher voltage drops may result. Thoroughly clean all connections in any part of the circuit showing excessive
voltage drop.

WARNING Many troubleshooting procedures
present hazards that can result in severe personal injury or death. Only qualified service
personnel with knowledge of fuels, electricity,
and machinery hazards should perform service
procedures. Review Safety Precautions.

[C]
BATTERY CHARGING CHECK
With the engine running, check the DC voltmeter
(control option). The 12-volt system should read
13.5 to 15 volts.

[A]

The power source is a belt-driven alternator. The
charge rate/voltage is determined by a voltage regulator located inside the control box.

BATTERY CHECK (BT1)
Check the battery charge condition with a hydrometer. Electrolyte specific gravity should be about
1.260 for a fully charged battery at 80°F (27°C). If
not, add distilled water to keep electrolyte at proper
level, then recharge the battery. If the battery will
not recharge, replace it.

Improper output may be caused by a loose drive
belt, poor terminal connections, broken wires, bad
regulator or alternator. Checkout procedures for
the regulator and alternator are found in the engine
service manual. The charge circuit is protected by
circuit breaker CB13.

If the battery loses excess water, the charge rate
may be too high. If the battery charge is not maintained, the charge rate may be too low. See procedure [C].

If the output voltage is high (over 15 volts), check for
loose or corroded voltage regulator leads. If this
does not correct the problem, the regulator is probably shorted and should be replaced.

Ignition of explosive battery gases
can cause severe personal injury. Do not permit
any flame, spark, cigarette, or other ignition
source near the battery.

[D]

WARNING

START SOLENOID CHECK (K11)
1. Apply battery positive (B+) to the terminal
marked S.

[B]

2. Connect a ground wire to the solenoid terminal
marked I. The solenoid should activate.

BATTERY CABLE CHECK
With the starter motor running, check these voltage
drops:

3. If the contacts are good, battery voltage should
be read between terminal 1 and ground. The
voltage drop measured across the contacts
should never exceed one volt in circuit application.

1. From the battery negative post (not the cable
clamp) to the cylinder block

3-1

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3. Open and close switch while observing the
ohmmeter. A normally open (NO) switch
should indicate infinite resistance when open
and continuity when closed. A normally closed
(NC) switch should indicate continuity when
closed and infinite resistance when open.

[E]
HEATER (GLOW PLUG) RELAY CHECK
(K13)
1. Connect the relay coil voltage across the relay
coil terminals. The relay should activate if coil
is okay.

4. Replace switch if defective.

[H]

2. Connect a voltage source to one side of relay
contacts.

POWER RELAY CHECK (A11-K12)

3. Connect a voltmeter to other side of relay contact and voltage source. If voltage appears
when relay energizes, the contact is good. The
voltage reading appears in reverse order when
checking normally closed (NC) contacts.

Make certain that the genset starting battery is good
before beginning this check.
1. Unplug CB12-2A from the circuit breaker. Note
the markings on the wire to select the correct
one.

[F]

2. Locate S6 (oil pressure switch) on the genset
(see Figure 2-2). Find the grounded side of S6,
using a continuity tester.

FUEL SOLENOID CHECK (K14)
If there is fuel to the injection pump, but no fuel at the
injection nozzle, the fuel solenoid may be defective.

3. Use a jumper to ground the non-grounded side
of S6.

To check solenoid operation, watch for solenoid actuation when B+ is applied (start switch in start or
run position). If there is no actuation when B+ is applied, the fuel solenoid must be replaced. When B+
is removed, the solenoid must de-activate.

4. Use a second jumper from the B+ terminal on
the control board to apply B+ to the SW B+
(switched B+) terminal. Fuel pump E5 should
start and run.
5. Remove the B+ jumper. If the fuel pump continues to run, K12 is good. If the fuel pump stops,
K12 has failed and the A11 control board
should be replaced.

[G]
START/STOP SWITCH CHECK (S11)
1. Remove battery B+ cable.

6. Push the genset STOP button.

2. Place ohmmeter leads across switch.

7. Remove the jumpers and reconnect CB12-2A.

3-2

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4. Generator/Voltage Regulator
erator cooling air which is drawn in through the end
bell and discharged through an outlet in the blower
end.

GENERAL DESCRIPTION
The YK generator (Figure 4-1) is a four-pole, revolving field, brush-type design with drip-proof
construction.

A ball bearing in the end bell supports the outer end
of the rotor shaft. The end bell is attached with four
studs that thread into the generator adapter casting.
The genset brushes are mounted in the end bell
(see Figure 4-2).

The generator rotor is directly coupled to the engine
flywheel with a rigid drive disc. Engine speed determines generator output voltage and frequency. A
centrifugal blower on the drive disc circulates genSTATOR
ASSEMBLY

GENERATOR
ADAPTER

FAN
GUARD

END BELL
COVER

ROTOR
ASSEMBLY
OUTPUT AND
CONTROL LEADS
COLLECTOR
RINGS
GENERATOR
DRIVE DISK

GENERATOR
DRIVE HUB

END BELL ASSEMBLY
(SEE FIGURE 4−2 FOR
BRUSH CONFIGURATION)

STATOR
ASSEMBLY

STATOR
WRAPPER

END
BEARING

GENERATOR FAN

FIGURE 4-1. YK SERIES GENERATOR

4-1

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LEAD (F1 TO
VR1−1)

LEAD (F2 TO
VR1−2)

O−RING
BRUSH BLOCK
ASSEMBLY

FIGURE 4-2. GENSET END BELL WITH BRUSHES

4-2

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by any means, is strictly prohibited.

FIGURE 4-3. SINGLE-PHASE GENERATOR SCHEMATIC

4-3

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by any means, is strictly prohibited.

FIGURE 4-4. THREE-PHASE GENERATOR SCHEMATIC

4-4

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by any means, is strictly prohibited.

which in turn supplies the field. Rated output
voltage is thereby maintained as the load varies.

GENERATOR OPERATION
Refer to Figures 4-3 and 4-4, the generator schematics, while working through the following description.

ELECTRONIC VOLTAGE REGULATOR

1. Voltage regulator VR1 (three-phase: VR21)
supplies DC to the field winding (F1 - F2 leads)
through brushes and slip rings, thereby establishing a revolving 4-pole magnetic field. The
battery is connected during startup to initiate
field excitation. Voltage regulator VR1 supplies
field current during operation. Rated output
voltage is maintained as the generator load
varies, by varying field current to maintain field
strength proportional to the load.
2. The revolving magnetic field induces AC in the
stator windings (T1 - T2 and T3 - T4) which are
connected to the load.
3. Under light load, the stator windings can supply
sufficient current for the field to maintain rated
output voltage.
4. As the load increases, load currents increase,
resulting in a proportional increase of current,

The voltage regulator controls the output of the generator so that a constant voltage is maintained under varying load conditions.
Only the basic functions of the regulator are described (Figure 4-5). Voltage from quadrature windings Q1/Q2 supply power to the voltage regulator itself. The voltage regulator in turn supplies an excitation voltage (F1/F2) that is directly proportionate
to the output voltage (L1/L0) it senses. Any
changes in the generator output voltage produce a
corresponding change in the excitation voltage provided by the regulator.
On the HDKAG, the voltage regulator assembly includes a potentiometer which enables a slight degree of output voltage adjustment. The voltage regulator assembly contains no user-serviceable
parts. If the assembly fails, it must be replaced.

VOLTAGE ADJUST: Trim pot adjusts output
voltage level. Turn pot clockwise to increase
voltage.
Turn pot counterclockwise to
decrease voltage.

BOARD SHOWN
WITHOUT COVER

FIGURE 4-5. ADJUSTMENTS ON GENSET VOLTAGE REGULATOR BOARD

4-5

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4. Install the new brushes and springs in the holder and keep them in place during assembly by
inserting a piece of wire through the holder, as
shown in Figure 4-7.
5. Install the brush holder. After tightening the
mounting screws, pull out the brush retaining
wire.
6. Connect the F1 lead to the inner brush terminal
(nearest the rotor windings). Connect the F2
lead to the outer brush terminal (nearest the
end bell).

GENERATOR SERVICE
Always disconnect the battery cables (negative [-]
first) from the battery to prevent accidental starting
of the set while servicing the generator.
WARNING Accidental starting of the set while
working on it can cause severe injury. To prevent accidental starting, disconnect the battery
cables (negative [-] first) from the battery.

The negative (-) cable is always disconnected
first, and connected last, to prevent arcing if a
tool accidentally touches the frame or other
grounded metal parts of the set while disconnecting or connecting the positive (+) cable.
Arcing can ignite the explosive hydrogen gas
given off by the battery, and cause severe injury.

Slip Ring Inspection/Replacement
Inspect the slip rings for grooves, pits or other damage. If dust has accumulated on any generator
components, they can be cleaned with filtered lowpressure air.
1. Examine the slip rings while servicing the
brushes.
2. If the rings need cleaning or service, remove
the rotor from the generator and dress the rings
on a lathe.

Brush Inspection/Replacement
The generator should be inspected for brush wear
and cleaning every six months.
WARNING Accidental starting of the generator
set can cause severe personal injury or death.
Stop the generator set and disable by disconnecting the starting battery cables (negative [-]
cable first) before inspecting the generator.

Dressing the slip rings on a lathe
improperly may damage the generator rotor.
Make certain that only an experienced technician performs this job.
CAUTION

1. Remove the access cover for the brush assembly.
2. Check the brushes for wear with a piece of wire
marked off 1 inch (25 mm) from one end (Figure 4-6). Replace the brush and the spring if
the wire goes into the brush holder 1 inch or
more.
3. To replace brushes, remove the brush holder
by disconnecting the two leads to the holder
and removing the two mounting screws.

Generator Bearing
Inspect the bearing for evidence of outer case rotation every 1000 hours of use. The bearing should
be replaced every five years, because the bearing
grease gradually deteriorates due to oxidation.
Replace the O-ring if it shows evidence of wear or
deterioration. Renew grease if necessary (moly
only).

4-6

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SPRING

BRUSH

GENERATOR
BEARING

1 INCH
MEASURING
WIRE

WIRE

ES1676

BRUSH BLOCK
ASSEMBLY

FIGURE 4-6. CHECKING GENERATOR BEARING
AND BRUSH BLOCK

HOLDER

FIGURE 4-7. BRUSH REPLACEMENT

4-7

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5. Lift the rear of the set and place a wooden block
under the generator adapter to hold the stator
and housing in place. Make certain that the engine-to-generator adapter (bolted to the engine) is propped up high enough for the generator adapter assembly (bolted to the generator) to clear the rear genset mounts when it is
pulled off the set. A block approximately 3.5
inches wide (standard 2 x 4 lumber width) will
hold the adapter high enough. Remove the two
rubber vibration isolators whose bolts were removed in the last step.

GENERATOR DISASSEMBLY/ASSEMBLY
The following sections describe the disassembly
and reassembly procedures for the generator. Figure 4-8 illustrates generator disassembly.

Generator components are heavy
and can cause severe personal injury if dropped
during service. Be careful, use appropriate lifting techniques, keep hands and feet clear during service, and use the recommended service
procedures.
WARNING

6. Remove the end bell cover and disconnect F1
(outer) and F2 (inner) lead wires from the brush
holder terminals.

Note that the control box and air cleaner assembly
need not be removed from the set to disassemble the
generator. These components may remain attached
to the stator housing, and will be removed with it.

7. Pull each brush away from the commutator
rings and insert a piece of stiff wire into the
small hole in the brush holder. See Figure 4-7.

Disassembly
1. Remove the generator set from the vehicle and
place it on a sturdy work bench. Refer to Section 1 of this manual for removal guidelines.

Note that the brushes may be secured (as described in the last two steps) at any convenient
point during this procedure.

8. Remove four nuts and lock washers from the
generator stud bolts. Remove the end bell cover and pry the end bell free of the rotor bearing.
Be careful not to damage the brush holder.

WARNING Accidental starting of the set
can cause severe personal injury or death.
Disconnect the battery cables, negative (-)
lead first, when repairs are made to the engine, controls or generator.

9. Pull the stator/wrapper assembly with the control boxes off the rotor and away from the engine. Set it aside.

2. Remove the cover from the AC control box and
disconnect all stator leads (Q1-Q50/60,
T1-T2-T3-T4, F1-F2, S1-S2). Disconnect
leads at the load circuit breaker(s). If the lead
markings do not clearly identify reconnection,
mark the leads with tape.

10. Remove the four bolts that hold the generator
adapter and fan guard to the engine-to-generator adapter. Pull the adapter/guard assembly
off the adapter and set it aside.
11. Loosen the six bolts that hold the rotor drive
disk to the engine flywheel. Loosen these bolts
in an alternating pattern, so that the drive disk
does not bend from the weight of the rotor.
12. Pull the rotor, fan and drive disk assembly off
the flywheel and set them aside.

3. Remove the bonding strap between the stator
assembly and the drip pan.
4. Loosen and remove the two bolts that extend
through the rear genset mounts (under the stator housing).

4-8

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END BELL
ASSEMBLY

BRUSH
BLOCK
O−RING

FAN

STUD BOLT
(1 OF 4)

SPRING
BRUSH

END
BEARING

END BELL
COVER

ROTOR
ASSEMBLY

ENGINE−GENERATOR
ADAPTER
MOUNTING
FOOT
STATOR
ASSEMBLY

xES2095s

FIGURE 4-8. GENERATOR DISASSEMBLY/REASSEMBLY

4-9

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2. Apply Loctite #680 adhesive to the shaft mating
surface.
3. Apply Loctite #747 activator to the bearing mating surface.
4. Install the bearing and allow ten minutes curing
time before handling the assembly.

Rotor Disassembly
1. Place the rotor assembly on a wood block in the
horizontal position. The drive disc and fan
should not be resting on anything, or distortion may occur.
2. Remove the six bolts that hold the drive disk
and fan to the rotor hub. Remove the drive disk
and fan.

Rotor Reassembly
After necessary service checks and repairs are
made, the rotor and generator are reassembled using the reverse procedure of disassembly except for
the rotor as noted below. Regrease the O-ring using moly grease only. Apply required torque value
shown in Figure 4-9.

3. Use a gear puller to remove the end bearing
from the rotor shaft.

The end bearing will be damaged if pulled on the outer race. If the bearing must be removed, replace it; this bearing should not be reused.
CAUTION

CAUTION The drive disk will be damaged if the
bolts are tightened and it is not properly centered. Center the disk accurately before beginning to tighten the drive disk.

Rotor Bearing Replacement
1. Clean the bearing and shaft mating surfaces.

4-10

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COLLECTOR
RINGS

ROTOR
WINDINGS
GENERATOR
DRIVE DISK
REMOVE SIX BOLTS AND
WASHERS TO REMOVE DRIVE
DISK FROM HUB: TORQUE TO
25−29 N−M WHEN REPLACING

GENERATOR
DRIVE HUB

END
BEARING
ROTOR
ASSEMBLY

GENERATOR
FAN

FIGURE 4-9. ROTOR ASSEMBLY COMPONENTS

4-11

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Blank Page

4-12

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A. NO AC OUTPUT VOLTAGE AT RATED ENGINE RPM

GENERAL
This section contains troubleshooting information
for the HDKAG generator and voltage regulator.
Make the following visual checks before starting:

B. UNSTABLE OUTPUT VOLTAGE, ENGINE
SPEED STABLE

• Check any modification or repair that was done
since the last satisfactory operation of the set.
Verify that it was done properly.

C. OUTPUT VOLTAGE TOO HIGH OR TOO
LOW

• Check to see that generator leads are connected correctly. Also check the voltage regulator and control component connectors. A
loose, contaminated, or misplaced wire connection can be detected by close inspection.

D. UNBALANCED OUTPUT VOLTAGE
To troubleshoot a problem, start at the upper left
corner of the chart that corresponds to the problem,
and answer all questions either YES or NO. Follow
the chart until the problem is found. Perform the referenced test or adjustment procedures in the Generator/Regulator Tests section.

• Check for an open circuit breaker. If the breaker is open, check for an overloaded circuit and
correct load problems before resetting the
breaker.

TROUBLESHOOTING PROCEDURES

Components referenced in the flow charts, tests
and adjustment procedures are found in the schematics and wiring diagrams in Section 9 of this
manual.

Determine the type of problem, then refer to the corresponding flow chart (A, B, C, or D) for troubleshooting procedures.

5-1

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FLOW CHART A. NO AC OUTPUT VOLTAGE AT RATED ENGINE RPM
WARNING Many troubleshooting procedures present hazards that can result in severe personal
injury or death. Only qualified service personnel with knowledge of fuels, electricity, and machinery hazards should perform service procedures. Review Safety Precautions.

START

Are load circuit breakers closed?

Locate cause of overload and correct as required. Reset breaker, or replace if bad.

no

yes
Check continuity of circuit breakers and
replace if necessary. Is circuit open between brush block and voltage regulator?

yes

Check for continuity and correct if circuit is
open.

no
Test field voltage per TEST [A]. Is
there correct field voltage?

yes

Perform TEST [D].

yes

Release brushes if jammed in holder. Clean
slip rings if dirty.

no
Are brushes stuck in holder or not
making good contact with slip rings?
no
Examine brush block connections. Are F1
and F2 leads installed on correct terminals?

no

Connect brush leads to correct terminals.

yes
Test continuity of rotor, stator per Tests
[B], [C]. Are there opens or grounds?

Replace component if defective.

yes

5-2

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FLOW CHART B. UNSTABLE VOLTAGE, ENGINE SPEED STABLE
WARNING Many troubleshooting procedures present hazards that can result in severe personal
injury or death. Only qualified service personnel with knowledge of fuels, electricity, and machinery
hazards should perform service procedures. Review Safety Precautions.

START

Are there any broken wires or loose connections on voltage regulator assembly?

yes

Repair as required.

no

Repair wiring or replace as required.

no

Repair or replace as required.

no
Check wiring harness from regulator assembly to end bell per TEST [F]. Check OK?
yes
Inspect brushes per procedure in Manual
Section 4. Brushes OK?
yes
Replace the voltage regulator per procedure
[E].

CAUTION A new voltage regulator can be damaged by malfunctioning components. Do not
install a new voltage regulator until all other
problems have been located and corrected.

5-3

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FLOW CHART C. OUTPUT VOLTAGE TOO HIGH OR TOO LOW
WARNING Many troubleshooting procedures present hazards that can result in severe personal
injury or death. Only qualified service personnel with knowledge of fuels, electricity, and machinery hazards should perform service procedures. Review Safety Precautions.

START

Is engine running at correct RPM?

no

Set RPM per instructions in appropriate
engine manual.

yes

Set control per Voltage Adjustment [G].

yes

Remove part of the set load.

yes

Are generator output leads properly connected? See TEST [H].

yes
Does adjustment of Voltage Adjust control on the regulator board result in correct output voltage?
no
Is the set AC output overloaded?
no
Are voltage regulator connections secure?

yes
CAUTION A new printed circuit board can be
damaged by malfunctioning components within
the control. Do not install a new PC board until all
other problems have been located and corrected.

5-4

Perform procedure [D]. If correctly functioning rotor/stator indicates a bad voltage regulator, replace it per procedure
[E].

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FLOW CHART D. UNBALANCED GENERATOR OUTPUT VOLTAGE
WARNING Many troubleshooting procedures present hazards that can result in severe personal
injury or death. Only qualified service personnel with knowledge of fuels, electricity, and machinery
hazards should perform service procedures. Review Safety Precautions.

START

Remove load at generator terminals. Is
output still unbalanced?

no

Check for correct grounding of generator
and load.

no

Correct as necessary.

no

Replace stator assembly.

yes
Are generator leads connected and
grounded properly? See Test [C].
yes
Is generator stator winding continuous
per TEST [C]?
yes
Check load for ground faults and correct
as necessary.

5-5

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Blank Page

5-6

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Section 6. Generator/Regulator Tests
GENERAL

[B] TESTING GENERATOR ROTOR

The following tests and adjustments can be performed without disassembly of the generator.
These procedures should be used for testing the
generator components and the regulator in conjunction with the Troubleshooting Flow Charts in the
Generator/Regulator Troubleshooting section.

The generator circuits can be tested without having
to disassemble the generator. It is recommended
that an ohmmeter be used to check for open circuits
and an insulation resistance meter for grounded circuits. An ohmmeter can be used to check for
grounded circuits, but it may not be able to detect
marginal insulation breakdown.

WARNING Many troubleshooting procedures
present hazards that can result in severe personal injury or death. Only qualified service
personnel with knowledge of fuels, electricity,
and machinery hazards should perform service
procedures. Review safety precautions on inside cover page.

MEGGER OR
INSULATION
RESISTANCE
METER

[A] TESTING FIELD VOLTAGE
Field voltage can be tested at the brush holder terminals with a DC voltmeter. Field voltage should fall
between 18 and 60 volts. Test at no load and at full
load. See Figure 6-1.

CONNECT LEADS
BETWEEN EACH RING
AND ROTOR SHAFT
LEAD (F2
TO VR1−2)

TEST POINTS

ES2068s

LEAD (F1
TO VR1−1)

FIGURE 6-2. TESTING ROTOR FOR GROUNDS

Testing for Grounds
Check for grounds between each slip ring and the
rotor shaft, Figure 6-2. Use a Megger or insulation
resistance meter which applies 500 VDC or more at
the test leads. Perform test as follows:
1. Isolate the rotor windings by disconnecting the
two leads to the brush holder.
2. Connect test leads between each ring and the
rotor shaft in turn. Meter should register
100,000 ohms or greater.
BRUSH
BLOCK
ASSEMBLY

3. If less than 100,000 ohms, rotor is questionable. Thoroughly dry the rotor and retest.

FIGURE 6-1. FIELD VOLTAGE TEST POINTS

4. Replace a grounded rotor with a new identical
part.

6-1

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[C] TESTING GENERATOR STATOR

Testing for Open or Shorted Windings
Perform this test with an accurate meter such as a
digital ohmmeter.
1. Isolate the rotor windings by disconnecting the
two leads to the brush holder.

Isolate the stator windings by disconnecting all six
stator leads. Test for open circuits between T1-T2,
T3-T4 and Q1-Q2, and for grounded circuits between T1, T3 and B1 and the stator laminations or
other unpainted grounding point.

2. Using ohmmeter, check resistance between
F1 and F2 by connecting leads between the F1
and F2 slip rings, Figure 6-3.

Using proper test equipment, check the stator for
grounds, opens, and shorts in the windings.

Rotor resistances (measured at 25° C) are:

Testing for Grounds

Standard single-phase: 17.2 ohms
Standard three-phase: 19.4 ohms
Extended-stack three-phase: 22.5 ohms
Extended-stack three-phase “husky”:
25.5 ohms

Some generators have ground connections to the
frame. Check wiring diagram. All stator leads must
be isolated for testing.
Use a megger or insulation resistance meter which
applies not more than 500 VDC to the test leads
(Figure 6-4). Test each stator winding for short to
laminations. A reading less than 100,000 ohms indicates a questionable stator. Thoroughly dry the
stator and retest.

If there is a large difference, replace the defective rotor with a new, identical part.

DIGITAL
OHMMETER

CONNECT LEADS BETWEEN
F1, F2 SLIP RINGS

CONNECT LEADS BETWEEN
EACH WINDING AND GROUND

ES2070s

ES2069s

FIGURE 6-4. TESTING STATOR WINDING
FOR GROUNDS

FIGURE 6-3. TESTING ROTOR FOR AN
OPEN CIRCUIT

6-2

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[D] DYNAMIC ROTOR/STATOR TEST

Testing for Open or Shorted Windings
Test for continuity between coil leads as shown in
Figure 6-5; all pairs should have equal resistance.
Use an accurate instrument for this test such as a
Wheatstone Bridge.

The following procedure serves as a functional voltage regulator check, by determining if the problem
is in the voltage regulator or in the generator. The
voltage regulator is temporarily replaced with a
12-volt battery (the genset starting battery is usable
here); 12 volts applied to the F1/F2 exciter stator
should produce approximately 125 volts generator
output voltage at L1 and L2, with no load.

Stator resistances (measured at 25° C) are:
Standard single-phase:
T1-T2, T3-T4: 0.221 ohms
Q1-Q60: 1.997 ohms
Q1-Q50: 2.405 ohms
Standard three-phase:
T1-T4, T2-T5, T3-T6,
T7-T10, T8-T11, T9-T12: 0.505 ohms
Q2-T11: 0.252 ohms
Extended-stack three-phase:
T1-T4, T2-T5, T3-T6,
T7-T10, T8-T11, T9-T12: 0.153 ohms
Q2-T11: 0.305 ohms
Extended-stack three-phase heavy-duty:
T1-T4, T2-T5, T3-T6,
T7-T10, T8-T11, T9-T12: 0.107 ohms
Q2-T11: 0.214 ohms

WARNING Electrical shock can cause severe
personal injury or death. Do not touch electrical
wiring or components during testing. Disconnect electrical power by removing starting battery negative (-) cable before handling electrical
wiring or components.

Use a sharp voltage probe and touch it carefully to
the connector pins or output terminals when making
these tests.
1. Stop the generator set.
2. Unplug the voltage regulator from the wiring
harness.
CAUTION Failure to unplug the voltage
regulator at this point in the procedure
could lead to equipment damage.

If a winding is shorted, open or grounded, replace
the stator assembly. Before replacing the assembly, check the leads for broken wires or insulation.

3. Using jumpers and a spare plug or other connector, connect a 12-volt battery to the F1/F2
terminals as illustrated in Figure 6-6.
4. Start the generator set. Use a voltmeter to
measure the outputs at J4-4 - J4-6, L1 - L2, L1 L0, L2 - L0, Q60 - Q1 (50 Hz sets: Q50 - Q1),
and S1 - S2. The output voltages should read
as follows (all voltages apply to both 50 Hz and
60 Hz sets):
J4-4 - J4-6: 62 VAC ± 20 VAC
L1 - L2: 125 VAC ± 20 VAC
L1 - L0: 62 VAC ± 20 VAC
L2 - L0: 62 VAC ± 20 VAC
Q60 - Q1: 75 VAC ± 20 VAC
(50 Hz sets) Q50 - Q1: 75 VAC ± 20 VAC
S1 - S2: 62 VAC ± 20 VAC

CONNECT LEADS
BETWEEN PAIRS
OF STATOR
WINDING LEADS

ES2071s

If these voltages are measured, then the generator is operating correctly and the problem is
elsewhere.

FIGURE 6-5. TESTING STATOR WINDING
RESISTANCE

6-3

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MEASURE
125 VAC

MEASURE
62 VAC

MEASURE
62 VAC

−
+

MEASURE
62 VAC

MEASURE
75 VAC

APPLY
12 VDC

MEASURE
62 VAC

MEASURE
75 VAC

FIGURE 6-6. DYNAMIC ROTOR/STATOR TEST

6-4

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sure the generator set has stabilized and is running
at the correct speed (frequency). The regulator is
adjusted with the set running.

[E] VOLTAGE REGULATOR
REPLACEMENT
Use the following procedure for replacing the AC
voltage regulator assembly.

WARNING Accidental starting of the set can
cause severe personal injury or death. Disconnect both battery cables, negative (-) cable first,
when repairs are made to the engine, controls,
or generator.

1. Stop the generator set and disconnect the
starting battery leads, negative (-) lead first.
2. Unscrew the voltage regulator from the control
box.

WARNING Contact with high voltage can cause
severe personal injury or death. Do not touch
any exposed wiring or components with any
part of the body, clothing, tool or jewelry. Do not
use non-insulated tools inside the control.
Stand on an insulating mat or dry wood platform
when the control doors are open.

3. Disconnect the regulator from the wiring harness.
4. Remove the mounting screws from the old voltage regulator, then install the new regulator.
5. Reconnect the plug connection to the wiring
harness.

Output voltage adjustments are found on the voltage regulator board under the DC control box. A removable cover protects the board. See Figure 6-7.

6. Set voltage as outlined in [G] Voltage Adjustment.

[F]

1. Attach a voltmeter securely to the L1 and L2
leads.

WIRING HARNESS CHECK
Carefully check the wiring harness as follows:

2. Start the generator set and place a typical load
on its output.

1. Inspect all wires for breaks, loose connections,
and reversed connections. Refer to applicable
wiring diagram.

3. Use a flat-blade screwdriver to set the voltage
adjust potentiometer for correct voltage.

2. Remove wires from terminals at each end and
with an ohmmeter, check each wire end to end
for continuity or opens.

For most 60 Hz applications, the ideal setting is 117
VAC at 60-61 hz, measured at the power input of the
application. Retighten the locking nut when complete.

3. Using an ohmmeter, check each wire to other
wires and to ground for possible shorts or insulation breaks under areas covered by wrapping material.

Note that the voltage adjustment pot on the voltage
regulator board is a 10-turn potentiometer: it may
take several turns to change the voltage noticeably.

4. Reconnect or replace wires/harness according
to applicable wiring diagram.

[H]

[G]

RECONNECTION

VOLTAGE ADJUSTMENT

Generator reconnection is dependent upon the
nameplate code. See Section 8 for reconnection
diagrams.

This section describes adjustment of the genset
output voltage. When checking output voltage, be

6-5

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VOLTAGE ADJUST: Trim pot adjusts
output voltage level.
Turn pot
clockwise to increase voltage. Turn pot
counterclockwise to decrease voltage.

BOARD SHOWN
WITHOUT COVER

FIGURE 6-7. LOCATION, OUTPUT VOLTAGE ADJUSTMENT

6-6

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Section 7. Routine Maintenance
hours indicated, whichever comes first. Refer to the
Maintenance Procedures section for instructions. If
the generator set will be subjected to extremely hot
or dusty conditions, a more frequent maintenance
schedule may be necessary.

INTRODUCTION
This section describes routine maintenance procedures to be performed on the generator set. Most of
this information is duplicated in the Operator’s
Manual, publication #981-0137.
Many of the items in this section refer to the genset
engine: for more information, refer to the Engine
Workshop Manual.

WARNING Accidental starting of the generator
set during maintenance can cause severe personal injury or death. Disconnect both generator set starting battery cables, before performing maintenance. Remove the negative (-) cable
first to reduce the risk of arcing.

MAINTENANCE SCHEDULE
Perform each maintenance procedure at the time
period indicated or after the number of operating

TABLE 7-1. PERIODIC MAINTENANCE SCHEDULE

SERVICE THESE ITEMS
Inspect set
Check oil level
Check coolant level
Check fuel level
Check air cleaner dust cap (clean if required)
Check battery charging system
Check drive belt tension
Clean out spark arrester
Check battery specific gravity
Change crankcase oil and filter
Drain water/sediment from fuel filter
Check antifreeze
Clean generator assembly
Drain sediment from fuel tank
Clean crankcase breather
Check fuel shut-off linkage
Change fuel filter element
Check genset brushes
Change air cleaner element
Clean cooling system

Daily
or
after
8 hours
x1
x
x
x

SERVICE TIME
Weekly
Monthly 6 Months Yearly
or
or
or
or
after
after
after
after
50 hours 100 hours 250 hours 500 hours

x3

x
x
x4

x
x
x2
x
x
x
x5
x3
x
x
x
x3
x

1 - Check for oil, fuel, cooling and exhaust system leaks. Check exhaust system audibly and visually
with genset running and repair any leaks immediately.
2 - Perform after first 35 hours of operation on new genset.
3 - Perform more often in extremely dusty conditions.
4 - Visually check belts for evidence of slippage.
5 - Drain one cup of fuel to remove water and sediment.

7-1

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GENERATOR SET INSPECTION

Fuel leakage will create a fire hazard
which can result in severe personal injury or
death if ignited. While checking for leaks, do
not smoke or allow any spark, flame, pilot light
or other ignition source in the area. If any leaks
are detected, have them corrected immediately.
WARNING

Inspect the generator set daily or after every eight
hours of operation, whichever comes first. Check
the exhaust, fuel, and DC electrical systems as described below. Also check the mechanical condition of the set.

Engine Gauges (Remote Installation)

DC Electrical System

Check these gauges while the set is running.

With the genset off, check the battery terminals for
clean and tight connections. Loose or corroded
connections create resistance which can impede
starting. Clean and reconnect loose battery cables.
Always disconnect the negative battery cable first
and connect it last, to reduce the possibility of arcing.

Oil Pressure Gauge: Oil pressure should be 40 to
60 psi (276 to 414 kPa) when the engine is at operating temperature.
Coolant Temperature Gauge: Coolant temperature should be 165° to 195° F (74° to 91° C), depending on load and ambient temperature.

WARNING Ignition of explosive battery gases
can cause severe personal injury. Do not
smoke. Wear goggles, protective rubber gloves
and apron when servicing batteries.

DC Voltmeter: Battery voltage during operation
should be 14 to 15 volts.

Exhaust System

Mechanical

With the set running, inspect the entire exhaust system including the exhaust manifold, exhaust elbow,
muffler and exhaust pipe. Visually and audibly
check for leaks at all connections, welds, gaskets,
and joints. If any leaks are detected, shut down
the genset and do not operate until corrected.
Replace corroded exhaust components before
leaks occur.

Check for any signs of mechanical damage. Start
the set and listen for any unusual noises that may
indicate mechanical problems.
Check the mounting fasteners to make sure the set
is secure in its compartment. If an under-floor housing is used, make sure that the set is secured to the
housing. Check the condition of the housing components and make sure they are secure to the vehicle.

Inhalation of exhaust gases can result in severe personal injury or death. Inspect
exhaust system audibly and visually for leaks
daily. Repair all leaks immediately.
WARNING

Make sure that the generator set air inlet and outlet
areas are not blocked with debris.
Clean the generator set whenever dust and dirt begin to accumulate. Dust and dirt can usually be removed with a damp cloth. Steam cleaning may be
needed to remove road contaminants. Do not clean
the genset while the engine is running. Protect the
generator, air cleaner, control panel, and electrical
connections from cleaning solvents. Cleaning solvents can damage electrical connectors.

Fuel System
With the set running, inspect the fuel supply lines,
return lines, filters, and fittings for leaks. Check flexible sections for cuts, cracks and abrasions. See
that the fuel lines do not rub against anything that
could break them. Replace worn fuel line components before leaks occur.

7-2

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gine oil can cause cancer or reproductive toxicity. When adding, changing or working with
used oil, take care not to breathe, ingest or
come into excessive contact with these substances. Wash hands after use. Wear protective clothing and equipment. Provide adequate
ventilation.

OIL AND FILTER CHANGE
Change the oil and filter at the intervals listed in
Table 7-2. Use oil that meets the API classification
and SAE viscosity grade indicated in the previous
section.

Engine Oil Change

Oil Filter Change

Run the engine until thoroughly warm. Stop the engine, open the drain valve (Figure 7-1) and drain the
oil into a container. When completely drained, close
the valve and refill the crankcase with new oil.

Spin off the oil filter and discard it. Thoroughly clean
the filter mounting surface. Apply a thin film of oil to
the filter gasket, and spin the filter on until the gasket
just touches the mounting pad. Then turn an additional 3/4 turn. Do not over-tighten the filter.

WARNING Hot crankcase oil can cause burns if
it is spilled or splashed on skin. Keep fingers
and hands clear when removing the oil drain
plug and wear protective clothing.

With oil in the crankcase, start the set and check for
leakage around the filter gasket. Tighten the filter
only enough to eliminate leaks.

State or federal agencies have determined that prolonged contact with used enWARNING

OIL FILL

ALTERNATE OIL FILL AT
TOP OF CYLINDER
HEAD COVER (HIDDEN)

OIL
DIPSTICK

DRAIN
VALVE

OIL FILTER

FIGURE 7-1. ENGINE OIL

7-3

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Add coolant to the recovery tank (or separate expansion tank if equipped) to the full-cold level.

COOLING SYSTEM
The cooling system must be filled with coolant
before the genset can be operated. Cooling system capacity is listed in the Specifications section.

Start the engine, then remove the pressure cap and
monitor the coolant level. As trapped air is expelled
from the system, the coolant level will drop. Add
coolant to replace it. Replace the pressure cap
when the coolant level is stable.

Coolant Requirements
Engine coolant must inhibit corrosion and protect
against freezing. A 50/50 mixture of ethylene glycol
anti-freeze and water is recommended for normal
operation and storage. Use only a reliable brand of
antifreeze that contains a rust and corrosion inhibitor. The antifreeze must not contain a stop-leak
additive.

Coolant Level
Check the coolant level at the intervals specified in
the Periodic Maintenance Schedule. Check by observing the coolant level in the recovery tank (or
separate expansion tank if equipped) when the system is cold. See Figure 7-2 for a typical cooling system. Engine coolant is at the proper level when the
recovery tank level is between FULL and LOW
marks.

Do not exceed a 50/50 mixture of ethylene glycol
and water. A higher proportion of ethylene glycol
will alter the heat transfer properties of the coolant.
A 50/50 mixture will provide freeze protection to
-34° F (-37° C).
Water used for engine coolant should be clean, low
in minerals, and free of corrosive chemicals. Use
distilled or soft water if available. Avoid the use of
well water, which may contain minerals that can
clog the heat exchanger core and reduce cooling efficiency.

WARNING Coolant in a warm engine is under
pressure and can flash to steam causing severe
burns if the radiator cap or drain cock are
opened. Let the engine cool down before opening the radiator cap or drain cock.

Filling the Cooling System

The high engine temperature cutoff
will shut down the engine in an overheat condition only if the coolant level is sufficiently high
to physically contact the shutdown switch.
Loss of coolant will allow engine to overheat
without protection of shutdown device, thereby
causing severe damage to the engine. It is
therefore imperative that adequate engine coolant levels be maintained for operational integrity of the cooling system and engine coolant
overheat shutdown protection.
CAUTION

Verify that all drain cocks are closed and all hose
clamps are secure. Remove the cooling system
pressure cap and slowly fill the cooling system with
the coolant mixture.

Exceeding the recommended fill
rate can cause incomplete filling of the engine
block, leading to engine damage during warmup. Always follow the recommended fill procedure.
CAUTION

7-4

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HOSE IS CONNECTED AT
RADIATOR CAP
BRACKET

RECOVERY
TANK

OVERFLOW
HOSE

RADIATOR COOLANT DRAIN
(ON LOWER REAR CORNER OF
RADIATOR)
G1250s

CYLINDER BLOCK COOLANT DRAIN
(REAR OF GENSET ENGINE BLOCK
SHOWN WITHOUT SHEET METAL, EXHAUST PARTS)

FIGURE 7-2. COOLING SYSTEM COMPONENTS

7-5

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FAN BELT

Flushing and Cleaning

A loose fan belt can cause the engine to overheat.
The belt tension must be correct for the set to run
well.

Once a year, drain, flush and refill the cooling system with new coolant. To drain the system, open the
radiator coolant drain and the cylinder block drain
on the the rear (non-service access) side of engine.
See Figure 7-2.

First, remove the generator set’s starting battery
cables (negative [-] cable first).
WARNING Accidental starting of the set can
cause severe personal injury or death. Stop the
generator set and disable it by disconnecting
the starting battery cables (negative [-] cable
first) when maintaining or repairing the engine,
controls, or generator.

Contact with hot coolant can cause
severe burns. Do not bleed hot, pressurized
coolant from a closed cooling system.
WARNING

Chemical Cleaning: Rust and scale slow heat absorption and can block coolant flow. Clean the cooling system if rust and scale have collected on the
engine water jacket or in the heat exchanger. Use a
good cleaning compound and follow its instructions.

To reach the fan belt, remove the belt guard from the
front of the set. Do not operate the genset without the belt guard in place.
To adjust the belt, loosen the bolt that passes
through the long slot in the alternator mounting
bracket and slide the alternator until the tension is
right. See Figure 7-3.

Flushing: After cleaning, or before filling the system with new coolant, drain the system and fill with
clean water. Run the genset for 10 minutes, then
drain the system completely. Refill with the coolant
mixture.

Belt tension is correct when a finger pressure of 22
pounds (10 kg) at the middle of the belt deflects it
about 0.4 inch (10 mm).

CAUTION Never pour hot water into a cold engine or cold water into a hot engine. Doing so
can crack the head or the cylinder block. Do not
operate the unit without water for even a few
minutes.

PUMP/
FAN
PULLEY

ADJUST
TENSION
HERE

Thermostat
If the engine overheats or does not reach and maintain a minimum operating temperature, have the
thermostat removed and tested. Replace the thermostat with the gasket if necessary. See the Engine
Workshop Manual for instructions on thermostat removal and testing.

ALTERNATOR

Pressure Cap
Closed cooling systems use a pressure cap to increase the boiling point of the coolant and allow
higher operating temperatures. Replace the pressure cap every two years, or sooner if it malfunctions.

CS-1239

FIGURE 7-3. FAN BELT ADJUSTMENT

7-6

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Ignition of fuel can cause serious
personal injury or death by fire or explosion. Do
not permit any flame, cigarette, pilot light, spark
or other igniter near the fuel system.

Low fuel in the tank promotes condensation. In
warm weather, the fuel tank cools at night quicker
than the fuel. If the fuel level is low, the upper portion of the tank will cool more rapidly, forming condensation. In cold weather, the warm fuel returning
from the injectors heats the fuel in the supply tank. If
the fuel is low, condensation may form on the upper
part of the tank. To avoid condensation, fill the
fuel tank every time the genset is used.

Fuel Recommendation

Fuel Filter

Use ASTM 2-D (no. 2 Diesel) or ASTM 1-D (No. 1
Diesel) fuel with a minimum Cetane number of 45.
Number 2 diesel fuel gives the best economy and
performance under most conditions. Use number 1
diesel fuel when ambient temperatures are below
32° F (0° C), and during long periods of light engine
load.

The wrong fuel or dirty fuel will shorten the life of the
fuel filter. See the Periodic Maintenance Schedule
for the filter change interval.

FUEL SYSTEM
Use the best fuel available. Fuel quality is important
for dependable performance and satisfactory engine life.
WARNING

CAUTION Dirt or water in the system will cause
severe damage to both the injection pump and
the injection nozzles. It is extremely important
that the fuel be kept clean and free of water.

Use low sulfur content fuel which has a cloud point
at least 10 degrees below the lowest expected fuel
temperature. (Cloud point is the temperature at
which wax crystals begin to form in diesel fuel.)

Refer to the Periodic Maintenance Schedule for the
recommended filter change interval. However, if
the engine shows signs of fuel starvation (reduced
power or surging), the fuel filter must be changed.
This involves purging the fuel system of trapped air.
See Priming the Fuel System later in this section.

Fuel Handling Precautions
Prevent dirt, water or other contaminants from entering the fuel system. Filter or strain the fuel as the
tank is filled.

High Pressure Fuel System: The injection pump,
fuel injection lines and fuel injectors are the high
pressure fuel system. See Figure 7-4. The highpressure system is self-priming; trapped air is
forced out through the injection nozzles.

CAUTION Due to the precise tolerances of diesel injection systems, dirt or water in the system
will cause severe damage to both the injection
pump and the injection nozzles. It is extremely
important that the fuel be kept clean and water
free.

Low Pressure Fuel System
The electric fuel pump, fuel filter and injection pump
inlet comprise the low pressure fuel system. See
Figure 7-4. These components are normally
primed (purged of trapped air) at set installation. Be
sure to check the fuel level in the tank and that the
shutoff valve is open.

Condensation (water) can cause clogging of fuel filters as well as freezing problems. Water mixing
with the sulfur in the fuel forms acid which can corrode and damage engine parts.

7-7

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FUEL RETURN
LINE FITTING

INJECTION PUMP
FUEL INLET
INJECTION LINE
CONNECTING NUT

FUEL
FILTER

FUEL
INLET

FUEL
PUMP

FIGURE 7-4. FUEL SYSTEM

7-8

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1. Keep the battery case clean and dry.

AIR CLEANER

2. Make certain that the battery cable connections are clean and tight. Use a terminal puller
tool to remove the battery cables.

The air cleaner element (Figure 7-5) is a dry type
and should never have oil applied to it. Avoid touching the element except when cleaning it. Instructions for cleaning the element are on a label attached to the element. Change the element yearly,
or more often in extremely dusty conditions.
OUTLET

Remove corrosion from the battery terminal
connections. Wash the terminals with an ammonia solution or a solution consisting of 1/4
pound (about 100 grams) of baking soda in 1
quart (about 1 liter) of water. Be sure the vent
plugs are tight to prevent cleaning solution from
entering the cells. After cleaning, flush the outside of the battery and the surrounding areas
with clean water.

INLET

3. Identify the cable as positive (+) or negative (-)
before making the battery connections. Always connect the negative (-) cable last, to reduce the risk of arcing.

AIR CLEANER
ELEMENT

4. Maintain the electrolyte level by adding distilled
water. Fill each cell to the split-level marker in
the battery. The water component of the electrolyte evaporates, but the sulfuric acid component remains. For this reason, add water, not
electrolyte to the battery.

AIR CLEANER
BAND W/CUSHION
VALVE

5. Use a battery hydrometer to check the specific
gravity of the electrolyte in each battery cell
(Figure 7-6). Charge the battery if the specific
gravity measures less than 1.215. Do not overcharge the battery. Stop charging the battery
when the electrolyte specific gravity reaches
1.260, at approximately 80° F (27° C).

WING
BOLT

FIGURE 7-5. AIR CLEANER ASSEMBLY

BATTERY CARE
Service the battery at the intervals shown in the
maintenance schedule. Check the electrolyte level
more frequently during hot weather.

Batteries present the hazard of explosion that can result in severe personal injury. Do not smoke or allow any fire, flame, spark,
pilot light, arc-producing equipment or other
ignition sources around the battery area. Do
not disconnect battery cables while the generator set is cranking or running because explosive battery gases could be ignited.

SPECIFIC GRAVITY
READING SHOULD BE
1.260 AT 80° F (27° C)

WARNING

WARNING Battery electrolyte can cause severe eye damage and burns to the skin. Wear
goggles, rubber gloves and a protective apron
when working with batteries.

FIGURE 7-6. BATTERY CHECK

7-9

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by any means, is strictly prohibited.

CRANKCASE BREATHER

AC GENERATOR

Clean the crankcase breather element at the
scheduled intervals, using the following procedure
(see Figure 7-7).

Generator Brushes
The generator should be inspected for brush wear
and cleaning as required per the Periodic Maintenance Schedule. Perform this procedure according
to the steps in Section 4 of this manual.

1. Remove the cap nuts and gaskets from the top
of the cylinder head cover. Carefully remove
the cover. Avoid damaging the gasket.
2. From inside the cover, remove two machine
screws securing the breather element, plates
and shield.

Accidental starting of the generator
set can cause severe personal injury or death.
Stop the generator set and disable by disconnecting the starting battery cables (negative [-]
cable first before inspecting the generator.
WARNING

3. Clean the element in a suitable solvent. Dry the
element, then saturate with engine oil before replacing.

Generator Bearing

WARNING Many cleaning solvents present
a hazard of severe personal injury or death.
Follow the manufacturer’s instructions and
proceed with care.

Inspect the bearing for evidence of outer case rotation every 1000 hours of use. The bearing should
be replaced every five years, because the bearing
grease gradually deteriorates due to oxidation. See
Section 4 of this manual for information on the generator bearing.

4. If necessary, clean other breather components
in solvent before reassembling.

CAP NUT AND
GASKET

CYLINDER
HEAD COVER

FILLER CAP
AND GASKET

GASKET

BREATHER
PIPE JOINT

BREATHER
PIPE

ELEMENT
PLATE 2
BREATHER
ELEMENT
ELEMENT
PLATE 1
OIL
SHIELD

FIGURE 7-7. CRANKCASE BREATHER

7-10

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by any means, is strictly prohibited.

CLEANING THE GENERATOR SET

MUFFLER/SPARK ARRESTER

Clean the generator set at least every six months.
Dust usually can be removed with a damp cloth.
Some road contaminants may require steam cleaning. Do not steam clean the generator set while the
engine is running. When cleaning, protect the area
so spray is not directed into the generator, air cleaner, control box, fuel solenoid, or electrical connections. Do not clean with solvents; they can damage
electrical connectors.

The exhaust spark arrester mounted inside the muffler is necessary for safe operation. It must be periodically cleaned out for maximum efficiency, and to
meet Forest Service requirements (RV use). See
the maintenance schedule for cleaning intervals.

To clean the spark arrester, park the vehicle on a
non-flammable, washable surface, and remove the
1/8 inch pipe plug from the bottom of the muffler.
Run the generator set with a full load for five minutes. Stop the generator set and allow the muffler to
cool. Replace the pipe plug in the muffler. See Figure 7-8.

INITIAL STARTING AND CHECKS
WARNING Exhaust gas presents the hazard of
severe personal injury or death. Do not operate
the generator set inside any room or building.

If none of the fuel line junctions have been loosened
between the electric fuel pump and the injection
pump, the fuel system should not need priming.
However, if priming is necessary, it should be done
according to the following procedure.

Priming the Fuel System
CAUTION Priming the fuel system should only
be done by a skilled and experienced diesel
technician. Incorrect priming could lead to
equipment damage or faulty operation.

1. Turn off both DC breakers on the set control
box.
PIPE
PLUG

EXS−1190s

2. Disconnect the B+ lead to the fuel pump.
3. Use a clip lead to jumper B+ to the fuel pump.
Run the fuel pump for five to ten seconds until
the air is purged from the low-pressure fuel system.

FIGURE 7-8. EXHAUST MUFFLER

7-11

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by any means, is strictly prohibited.

Blank Page

7-12

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by any means, is strictly prohibited.

8. Wiring Diagrams
The electrical schematics and wiring diagrams that apply to the generator set covered in this manual are listed
below.
WIRING DIAGRAM

DRAWING NO.

PAGE

DC Control Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612-6635 . . . . . . . . . . . . . . . . . . . 8-2
AC Control Assembly (single-phase) . . . . . . . . . . . . . . . . 612-6637 . . . . . . . . . . . . . . . . . . . 8-3
AC Control Assembly (three-phase) . . . . . . . . . . . . . . . . 612-6732 . . . . . . . . . . . . . . . . . . . 8-4

8-1

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by any means, is strictly prohibited.

612-6635

Redistribution or publication of this document,
by any means, is strictly prohibited.

8-2

P4

J4

12

12

11

11

10

10

9

9

8

8

7

7

6

6

5

5

4

4 ( Q1 )

3

3 ( Q5 0 OR Q6 0 )

2

2

1

1

L1

L2
REF
DES
SEE NOTE 1

( 2)

1
2
3
G1
VR1

L0

T1

VR1
F1

Q6 0

Q1

A1

S1

Q5 0

DWG
QTY
SIZE
------

-----------

DESCRIPTION

WI RE HARNESS
LEAD ( F1)
LEAD ( F2)
GENERATOR
VOLTAGE REG- CAP AVR

1
1
1
1
1

AC
A1 1

2
T2
S2

F2

PART
N0

AC
NOTE:

T3

1. FROM J2-15 FOR FIELD FLASHING.

SEE NOTE 2

T4

2. QUADRATURE POWER CONNECTION Q60-60 HZ,
Q50-50 HZ UNITS.

MAIN
ARMATURE
STATOR

FIELD

SCHEMATIC

3. AVR REFERENCE VOLTAGE.
G1

7

6

8

5

9

4

10

3

11

2

VOL TAGE

1 1 0 / 2 2 0 V, 1 1 5 / 2 3 0 V & 1 2 0 / 2 4 0 V AS SHOWN
SEE RECONNECTI ON CHART FOR OTHER VOL TAGES

A

B

C

100
120

200
240

100/ 200
120/ 240

60

J

110
115

220
230

110/ 220
115/ 230

50

P

L1

L1

HZ CODE

L1
S1

S1

S1
Q1

12

T3

1

VR1

SCHEMATI C

P4/J4
SEE NOTE 3

L1

2

T1

L2

T4
T2

G1

T2

Q1
Q50 Q60

2

T1
T2

T1
Q50 Q60

2

T2

Q50 Q60

2

S2
L0

T3

T4

T4

S2

L0(N)

L0

L1

L2

L2

L0

L 1 L 0 ( N) L 2

T1 T2 T3 T4

T1 T2 T3 T4

DI AGRAM

L1

S2

T3

L0

1
Q
0
Q5

T3

L0

S1
S2
F1
F2
Q6
0

T4

T1

Q1

GND
SEE NOTE 2
A1

T1 T3 T2 T4
WIRING DIAGRAM

GND

1 1 0 / 2 2 0 V, 1 1 5 / 23 0 V & 1 2 0 / 2 4 0V AS SHOWN
SEE RECONNECTI ON CHART FOR OTHER VOL TAGES

GENERATOR
RECONNECTION CHART
612-6637

8-3

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by any means, is strictly prohibited.

612-6732

Redistribution or publication of this document,
by any means, is strictly prohibited.

8-4

Cummins Power Generation
1400 73rd Avenue N.E.
Minneapolis, MN 55432
763-574-5000
Fax: 763-528-7229
Cummins and Onan are registered trademarks of Cummins Inc.

Redistribution or publication of this document,
by any means, is strictly prohibited.



---

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