Generac Power Systems IM Series User Manual
Manual Part No. 75239
DIAGNOSTIC REPAIR
MANUAL
Air-Cooled
Recreational Vehicle
Generators
Printed in I! A.
FOREWORD
This DIAGNOSTIC REPAIR MANUAL has been prepared especially for the pur
pose of familiarizing service personnel with the operational analysis,
troubleshooting, testing, disassembly and repair of the Series NP45G, NP55G and
NP65G recreational vehicle generators.
Keep the Manual in a safe place and refer to it as often as necessary. The
Manual contains important technical data and should be referred to whenever the
need for such information arises.
Every effort has been expended to ensure the information in the Manual is
both accurate and current. However, the manufacturer reserves the right to
change, alter, or otherwise improve his product at any time without prior notice.
_________________TABLE OF
CONTENTS
Page
Wiring Diagram eind Eiectricai Schematic
Expioded View of Sheet Metai
Expioded View of Base and Puiiey..................................28
Exploded View of Generator and Panel
Electrical Formulas...........................................................32
Specifications....................................................................33
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......................
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26
30
Generator Fundamentals
Introduction........................................................................2
Electro-Magnetic Induction...............................................2
A Simple a-c Generator
A More Sophisticated a-c Generator
Generator Block Diagram.................................................3
....................................................
...............................
2
2
Introduction to Troubleshooting
Introduction.......................................................................4
Tools and Test Equipment
Rotor Rotational Speed....................................................4
Relationship of Voltage and Frequency
Generator a-c Connection System
Effects of Engine Power...................................................5
Effects of Dirt and Moisture on RV Generators
...............................................
.........................
..................................
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5
5
11
Troubleshooting the RV Generator
Introduction.......................................................................12
Problem No. 1- Engine Won’t Crank
Problem No. 2- Engine Cranks, Won’t Start
Problem No. 3- Engine Cranks and Starts, Shuts
Down When Start/Stop Switch is Released
Problem No. 4- Engine Starts Hard, Runs Rough
Problem No. 5- Engine Won’t Shut Down
Problem No. 6- Loss of Generator a-c Output................19
...............................
.......................
Engine Troubieshooting
General...............................................................................23
Checking Engine Compression
Check Engine Ignition
Check Carburetion............................................................23
Other Problems that Might Affect Engine Operation.. 23
4
......................................................
.......................................
Adjustments
General...............................................................................24
Engine Governor Adjustments
Voltage Regulator Adjustment.........................................24
5
Automatic Choke Adjustment
........................................
..........................................
...................
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Page
13
15
17
18
18
23
23
24
25
Operational Analysis of D-C Controi System
Introduction.......................................................................6
Circuit Condition- Engine Shut Down.............................6
Circuit Condition- Engine Cranking
Circuit Condition- Startup and Running
Circuit Condition- Normal Shutdown..............................8
................................
.........................
6
7
Insulation Resistance Tests
General...............................................................................9
The Hi-Pot Tester
Testing Stator Insulation..................................................9
Testing Rotor Insulation for Breakdown.........................10
Cleaning the Generator
Drying the Generator
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........................................................
9
10
10
GENERATOR FUNDAMENTALS
Introduction
It has long been known that a relationship exists between
magnetism and electricity. Revolving fieid a-c generators
depend on this relationship for their operation. The ser
vice technician must understand that relationship. This
section of your DIAGNOSTIC REPAIR MANUAL will
familiarize you with the basic fundamentals of generator
operation.
Electro-Magnetic Induction
A Magnetism Creates Electricity: - When a wire or
coii of wire is moved through a magnetic field, an electri
cal voltage is aeated in that wire. If the ends of the wire
are joined to complete a circuit, electrical current will flow
in the wire. The direction that current flows in the wire
depends on the polarity of the magnetic field.
B Current Flow Creates a Magnetic Field: - When
ever electrical current flows through a wire or coil of wire,
a magnetic field is created around that wire. The strength
of the field depends on the amount of current flow and
the number of coils or loops in the wire.
C A simple a-c generator consists of a spinning mag
netic field called a ROTOR and stationary coil of wire
called a STATOR. As the Rotor spins, its lines of mag
netic force cut across the stationary Stator. When the
ends of the Stator winding are connected across a load
(such as a light bulb) to complete the circuit, current will
flow through the circuit. In this simple generator, the
Rotor is a permanent magnet. The amount of voltage and
current flow induced into the Stator windings depends on
(a) the Rotor’s magnetic field strength, (b) Rotor rotational
speed, and (c) the number of turns of wire in the Stator.
A More Sophisticated a-c Generator
D A more sophisticated generator is equipped with a
Stator a-c power winding and a Stator excitation winding.
Regulated direct current from the excitation winding flows
through carbon brushes which slide on metallic slip rings
and then through the Rotor windings. Regulated current
flow through the Rotor creates a regulated magnetic field
strength. In turn, the regulated magnetic field strength
induces a regulated voltage into the stationary Stator;
winding. !
Generator Block Diagran^
E The Rotor (spinning fieid) is driven by the engine,
through a belt and pulley arrangement to maintain a fixed
operating speed. The Rotor’s magnetic field cuts across,
(a) a Stator a-c power winding, (b) a Stator excitation
winding, and (c) a Stator battery charge winding, to
induce a voltage Into those windings.
1. Stator Battery Charge Winding: Rectified direct
current output from this winding is delivered to the gen
erator’s 12-volts battery, to maintain battery state-ofcharge.
2. Stator a-c Power Winding:- The a-c output from this
winding is used to supply electrical power to connected
electrical loads.
3. Excitation Winding:- Output from this winding is
delivered to an Electronic Voltage Regulator, where it is
rectified and, based on a-c power winding sensing sig
nals, regulated. The regulated, rectified current flows
through the brushes and slip rings and into the Rotor
windings. Because the current flow is regulated, the
Rotor’s magnetic field strength Is regulated. In turn, be
cause the field strength is regulated, the voltage induced
into the Stator windings is regulated.
BATTERY
CHARGE
DIODE
00023
12 VOLTS
BATTERY
8
■T—f—L_r—\
Ü
Slip Rings \
Stator
Excitation
Winding
Stator a-c
Power
Winding
1
Stator a-c
Power
Winding
-r
Magnetic Field
Customer
Load
Connections
INTRODUCTION TO TROUBLESHOOTING
Introduction
A typical RV generator set does not have a large number
of parts. However, the parts are expensive. For that
reason, a parts replacement method of troubleshooting is
not cost effective. A basic understanding of generators is
essential to good troubleshooting, i.e., why they behave
or don’t behave as they should. This section will introduce
the technician to some of the fundamentals of
troubleshooting.
DANGER!: Recreational vehicle generators produce
extremely high and dangerous voltages. Use ex
treme care when working on or around the gener
ator. Contact with live wires and terminals will cause
extremely hazardous and possibly lethal electrical
shock. Only personnel who have been thoroughly
trained In the maintenance of RV generators should
attempt to troubleshoot, test, repair or service a gen
erator.
Tools and Test Equipment
The generator service technician should have a well
stocked tool box having a good selection of common hand
tools. Such a tool box should contain wrenches in both
metric and english sizes. Also recommended is a good
nut driver set.
A Volt-Ohm-Milliammeter:-An accurate volt-ohm-mil-
liammeter (VOM) is essential for the troubleshooting and
testing of generators. Simply having a VOM is not
enough. The technician must understand electricity, must
be familiar with electrical circuits, must be able to read
wiring diagrams/electrical schematics, and must know
how tio use the VOM.
B Frequency Meter:- This test device permits the gen
erator’s a-c ou^ut frequency, in HERTZ or CYCLES PER
SECOND, to be read. Measurement of frequency is re
quired for precise adjustment of engine-generator speed.
Also see ROTOR ROTATIONAL SPEED.
C Insulation Resistance Tester:- Also called a "Hl-
POT", this device permits generator Stator and Rotor
winding insulation to be tested for breakdown. Use the
Hi-Pot tester to test resistance between parallel stator
windings, between isolated windings, and the resistance
of all windings to ground. See also EFFECTS OF DIRT
AND MOISTURE ON GENERATORS.
NOTE: An electrical LOAD BANK Is also recom
mended for generator testing and adjustment. The
Load Bank permits a known electrical load to be ap
plied to the generator, for the purpose of testing/adjustlng unit operation under load.
__________________
Rotor Rotational Speed
The generator’s revolving field on Series NP45G, NP55G
and NP65G generators is a 2-pole type, having a single
north and a single south magnetic pole. The Rotor is en
gine driven through a belt and pulley arrangenrient. Such
a 2-pole Rotor must be operated at 3600 rpm to supply
an a-c frequency output of 60 Hz. The belt and pulley ar
rangement pro>4des a speed reduction, so that engine
speed can be reduced while driving the Rotor at its re
quired operating speed. The following formulae apply
when determining a-c frequency, Rotor rpm and number
of Rotor poles.
rpm X No. of Rotor Poles
Frequency = 2 x 60
2 X 60 X Frequency
RPM = No. of Rotor Poles
not be able to handle loads within the generator's rated
capacity. Problems with generator a-c output are oftencaused by an engine problem.
NOTE: A shorted condition In one or more con
nected electrical loads or In generator windings can
dramatically Increase the power demands on the
driving engine. Such shorted conditions may
present the same symptoms as an underpowered
engine.
________________________________________
2 X 60 X Frequency
Rotor Poles= rpm
Relationship of Voltage and Frequency
Engine governed speed and a-c voltage are adjusted with
no electrical loads applied to the generator (no-load).
That is, the a-c voltage is set at a fixed ratio to a-c
frequency. Recommended frequency and voltage set
tings are as follows:
Set Frequency to:
Set Voltage to;
*Llne-to-Neutral Voltage
60.5 to 63.5 Hz
121 to 127 volts*
Generator a-c Connection System
D Series NP45G, NP55G and NP65G RV generators
are equipped with dual Stator a-c power windings. These
windings may be connected in parallel to provide a 120votts a-c output as shown. Note that customer loads of
up to 30 a-c amperes may be connected across Wires T1
(red) and T2 (white); loads up to 20 a-c amperes across
wires T2 (white) and T3 (black).
E The generator’s a-c output leads may be reconnected
in series, to supply a dual voltage (120 and/or 240 volts)
a-c output. When this is done, connect 240 volts a-c
loads across T1 (red) and T3 (black); 120 volts across T1
(red) and T2 (white) or T3 (black) and T2 (white). T2 is
the neutral wire.
Effects of Dirt and Moisture oh RV
Generators
If moisture is permitted to remain in contact with gener
ator windings, some of that moisture may be retained in
cracks and voids of the winding insulation. This will
cause a reduced insulation resistance. However,
prolonged exposure to moisture resistance of stator and
rotor winding Insulation. Dirt can make the problem
worse, since it tends to hold moisture into contact with
windings. Salt (as from sea air) also makes the problem
worse, since salt will absorb moisture from the air. When
salt and moisture combine, they form a good electrical
conductor.
Because of the detrimental effects of dirt and moisture,
the generator should be kept as clean and as dry as
possible. Stator and rotor windings should be tested
periodically, using an insulation resistance tester (Hi-Pot
or megohmmeterX If insulation resistance is excessively
low, drying may be required to remove moisture. After
drying, a second test of insulation resistance is still low
after drying, replacement of defective windings may be
necessary.
Effects of Engine Power
The generator engine must develop sufficient power to
operate the generator under varying electrical loads. The
greater the wattage (amperage) demands ot connected
electrical loads, the greater the engine power needs. As
a general rule, approximately 2 engine horsepower is
ne^led for each 1000 watts (1.0 kW) of generator power
output.
If the generator’s wattage/amperage capacity is ex
ceeded, engine power may not be adequate to handle
the increased load. The result will be a decrease in
engine rpm, a corresponding decrease In generator a-c
output voltage and frequency, and internal generator
overheating.
A badly worn engine, one that has lost compression, or
one with defective fuel. Ignition or air Intake system may
OPERATIONAL ANALYSIS OF D-C CONTROL SYSTEM
Introduction
This section of your Manual is intended to familiarize the
reader with how the RV generator’s d-c control system
functions. The d-c control system provides the means to
obtain engine cranking, engine ignition and fuel flow, car
buretor choking, field boost and battery charging. If
problems with any of these functions are encountered,
the technician must have a working knowledge of how the
system operates.
Circuit Condition- Engine Shut Down
A With engine stopped, the circuit condition may be
described as follows:
1. Battery voltage is available to the normally-open
Starter Contactor (SC) contacts. The contacts are open
and the circuit is incomplete.
2. Battery voltage is available through a 15 amp Fuse (FI)
and to the normally open contacts of Control Relay (CR1).
These contacts are open and the circuit is incomplete.
3. Battery voltagte is available through Fuse (Ft), through
the normally-closed contacts of Control Relay (CR1),
through the Starter Contactor (SC) coil, and to the
Start/Stop Switch (SW1). However, the Switch contacts
are open and the circuit is incomplete.
4. Battery voltage is available through Fuse (F1), through
the Control Relay (CR2) actuating coil, and to the
Start/Stop Switch (SW1). However, the Switch contacts
are open and the circuit is incomplete.
5. Battery voltage is available to the Battery Charge Rec
tifier (BCR), via Wire #13, 15 amp Fuse (FI), Wire #15,
and to a Battery Charge Rectifier (BCR). However, BCR
diode action inhibits Current flow.
Circuit Condition- Engine Cranking
B When the Start/Stop Switch is held at its START posi
tion, the following sequence of events occurs
1. Start/Stop Switch closure connects the Control Relay
(CR2) and the Starter Contactor (SC) actuating coils to
frame ground.
2. The Starter Contactor (SC) energizes and its contacts
close to deliver battery voltage to (a) Starter Motor (SM)
and (b) a Choke Solenoid (CS) and (c) a Choke Module
(CM). The following events then occur:
a. Starter Motor (SM) energizes and the engine
cranks.
b. Battery voltage is delivered to the Choke Module
(CM), via Wire 16, the Choke Solenoid coil, and Wire
90. Choke Module (CM) action opens and closes
this circuit to ground at a rate dependent on ambient
temperature, to energize and de-energize the Choke
. Solenoid. Choke Solenoid (CS) opens and closes
the carburetor choke.
c. Battery voltage delivered to the Choke Module
(CM) is delivered to the generator Rotor windings via
a Field Boost Resistor and Diode (housed in the
Choke Module), Wire 4 and the Rotor brushes and
slip rings. This is field boost.
"1
-
7 ^
>-
&
►-
■t° Ife
-gAAAn
&
LEGEND
BCRc
. BATTERY CHARGE RECTIFIER
CIRCUIT BREAKER- 30 AMP
CB1 a
CIRCUIT BREAKER
CB2a
CH -
. CHOKE HEATER
CM c
.CHOKE MODULE
I CONTROL RELAY
CR1 -
. CONTROL RELAY
CR2-
. CHOKE SOLENOID
CS -
FI a
FUSE- 15 amp
FP -
FUEL PUMP
GROUND TERMINAL
QT HM c
. HOURMETER (Optional)
IGNITION MAGNETO
IMI IM2.
IGNITION MAGNETO
K3NmON SHUTDOWN
ISD.
RUN LIGHT
LI -
. LOW OIL PRESSURE, SWITCH
. LOP-
RESISTOR-1 ohm, 25 watt
R1 -
SC - STARTER CONTACTOR
SM - STARTER MOTOR
SW1 - START/STOP SWITCH
SPI - No. 1 SPARK PLUG
SP2 - No. 2 SPARK PLUG
TC o TERMINAL CONNECTOR
- WIRE NUT CONNECTION
d. Battery voltage is delivered through a diode
(housed in the Choke Module) and to the Wire 14 cir
cuit. Wire 14 is now electrically hot, to operate (a) a
Fuel Pump (FP), (b) a Choke Heater (CH), and (c)
an "Engine Run" lamp on the optional remote panel.
3. Control Relay (CR2) energizes, its nonnaiiy-closed
contacts open and the Wire 18 circuit is effectiveiy iso
lated from frame ground. Ignition can now occur, since
that circuit Is now open to ground.
4. With automatic choking, and with fuel flow and ignition
available, the engine will start.
5. Engine oli pressure buildup opens the Low Oil Pres
sure Swritch (LOP).
Circuit Condition- Startup and Running
C When engine fires and starts, the operator will release
the Start/Stop Switch. Circuit condition may then be
described as follows:
1. When a-c output from the generator's Battery Charge
Winding reaches approximately 9-12 volts a-c. Control
Relay (CR1) energizes and its normally open contacts
close, to deliver battery voltage to the Wire 14 circuit (Fuel
Pump and Choke Heater actions continue).
2. The Starter Contactor (SC) and Control Relay (CR2)
circuits to ground are opened.
3. Starter Contactor (SC) de-energizes and its contacts
open to effect the following
a. Starter Motor (SM) de-enerizes and cranking
ends.
b. Carburetor choking terminates.
c. Field Boost ends.
d. Power to the Wire 14 circuit through the Choke
Module ends.
4. Control Relay (CR2) de-energizes and its normallyclosed contacts close. However, the ignition circuit to
ground is held open by Low Oil Pressure Switch (LOP)
action and engine ignition continues.
5. Stator Battery Charge Winding (rectified) output is
delivered to the generator battery.
Circuit Condition- Normal Shutdown
D Closure of the Start/Stop Switch (SW1) to its STOP
position grounds the engine ignition circuit, ignition ter
minates and the engine shuts down. As engine speed
decreases. Low Oil Pressure Switch (LOP) closure main
tains the ignition ground condition.
r
INSULATION RESISTANCE TESTS
General
Refer to EFFECTS OF DIRT AND MOISTURE ON RV
GENERATORS (Page 5). The resistance of rotor and
stator windings should be tested periodically, using a
"Hi-Pot" resistance tester.
CAUTION!: When using the Hl-Pot (Insulation Resis
tance) tester, follow the tester manufacturer’s In
structions carefully. Improper use of the tester can
result in serious damage to the generator. Do not
apply voltage in excess to those recommended in
this Manual to Stator or Rotor windings.
____________
The Hi-Pot Tester
A The Hi-Pot tester shown is oniy one of many brands
available. It is equipped with an On/Off switch. Thepiiot
Lamp glows to indicate tester power is availabie. The
breakdown tamp will light to Indicate failure of the winding
being tested.
Testing Stator insuiation
6 Gain Access to Stator Leads: Remove screws that
retain the front panel to the panel housing. Remove the
generator cover. Inside the panel housing, locate the
Electronic Voltage Regulator and the 30-amp Circuit
Breaker (CB1).
4. Tum tester switch ON and check that Pilot Lamp is ON.
Then, set Voltage Selector Switch to 2000 volts. Observe
the BREAKDOWN lamp, wait one second, then turn
tester switch OFF.
C Disconnect Stator Leads: Disconnect Stator a-c
output wires 11 and 22 from the Electronic Voltage
Regulator terminals. Disconnect Stator Wire 33 from the
30-amp Breaker (CB1). Separate wires 22 and 44 at their
junction. Finally, disconnect Stator Excitation Wiriding
Wires 2 and 6 from the Electronic Voltage Regulator
terminals.
DANGER!: Follow the Instructions carefully. Wire
terminal ends must not be touching any part of the
generator when Hl-Pot voltage Is applied. Do not
exceed the recommended voltages. Apply voltage
to windings for a maximum of 1 second only.
Test All Stator Windings to Ground: Connect terminal
ends of Stator a-c output Wires 11, 22, 33, 44, 2 and 6
tightly together. Make sure no terminal end is in contact
with the generator frame. Then proceed as follows:
1 .Connect RED test lead of Hi-Pot tester to joined ter
minal ends of Wires 11,22, 33, 44, 2 and 6.
2. Connect the BLACK test lead to a dean, painted frame
ground (on generator Stator can).
3. Turn Hi-Pot tester switch OFF. Then plug tester into a
120 voits wall socket and set its Voltage Selector Switch
to 500 volts.
CAUTION!: IN STEP 4, DO NOT APPLY VOLTAGE
LONGER THAN ONE MINUTE.
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