Generac 86640 User Manual
Manual Part No. 86640
SERVICE
Manual
NP and IM Series
RECREATIONAL
VEHICLE AND
INDUSTRIAL MOBILE
AC GENERATORS
Liquid-Cooled 1.2 Liter
Gas Engine Models
CORPORATION
♦ P. O. Box 8
♦ Phone: (414) 544-4811
♦Waukesha, Wisconsin 53187
♦ FAX: (414) 544-4851
Original laaua (02/28/93)
Printed In U.SJt.
Foreword
PURPOSE OF MANUAL:
This Service Manual has been written and published by Generac Corporation to aid our Dealers" mechanics and
company service personnel In the maintenance, servicing, troubleshooting and repair of the products described
herein. All information, illustrations and specifications are based on the latest product Information available at the
time of publication.
Proper service and repair Is important to the safe, economical and reliable operation of all recreational vehicle
and Industrial mobile generators. Troubleshooting, testing and servicing procedures recommended by Generac
and described In this manual are effective methods of performing such operations. Some of these operations or
procedures may require the use of specialized equipment Such equipment should be used when and as
recommended.
Generac could not possibly know of and advise the generator service trade of all conceivable procedures by
which a service or repair might be performed or of the possible hazards and/or results of each method. We have
not undertaken any such wide evaluation. Therefore, anyone who uses a service procedure, method or tool not
recommended by Generac must first completely satisfy himself that neither his nor the product’s safety will be
endangered by the procedure or method selected.
USER’S RESPONSIBILITY:
It Is assumed that service personnel are familiar with the servicing procedures of these products or like or similar
products manufactured and marketed by Generac. It Is further assumed that such personnel have been trained In
the recommended servicing procedures for these products; and that such training Includes the use of mechanic’s
common hand tools, special Generac tools, and tools from other suppliers.
li
■-!
SAFETY:
When working on this product, it must be remembered that the generator AC electrical system produces high
and dangerous voltages that can cause severe electrical shock. Contact with high voltage terminals, bare wires,
etc., can result In dangerous and even fatal Injury.
To prevent accidental engine cranking and startup, always disconnect battery cables before working on or
around the generator.
Cover all openings Into the engine-generator, to prevent entry of foreign materials. Such materials could enter
the engine cylinders and cause extensive damage when the engine Is started.
It Is Important to note that the manual contains various DANGER, CAUTION and NOTE blocks. These should be
read carefully In order to minimize the risk of personal Injury or to prevent methods or practices from being used
which could damage equipment or render It unsafe.
FASTENERS:
Replacement fasteners must have the same measurements and strength as the fasteneres they will replace.
Numbers on the heads of metric bolts and on surfaces of metric nuts indicate their strength. Customary nuts do
not have strength markings. Mismatched or incorrect fasteners can cause damage, equipment malfunction or
possible Injury.
REPLACEMENT PARTS:
Many parts used on recreational vehicle generators and engines are designed and manufactured to comply with
rules and regulations established by the Recreational Vehicle Industry Association (RVIA), American National
Standards Institute (ANSI), and the National Fire Protection Association (NFPA). Strict compliance with such rules
and regulations help to minimize the risk of fire or an explosion. Use of any replacement part that does not comply
with such rules and regulations could result in fire or explosion hazard and should be avoided.
SERVICE
MANUAL
NP and IM Series
RECREATIONAL
VEHICLE &
INDUSTRIAL
TABLE OF CONTENTS
PART
1
2 ENGINE MECHANICAL
3 ENGINE LUBRICATION SYSTEM
4
5 GASOLINE FUEL SYSTEM
6 GASEOUS FUEL SYSTEM
7 ENGINE SPEED CONTROL SYSTEM
8
9 ENGINE DC ELECTRICAL SYSTEM
10
11 SPECIFICATIONS & ELECTRICAL DATA
ENGINE COOLING SYSTEM
ENGINE IGNITION SYSTEM
OPTIONS AND ACCESSORIES
TtTLE
THE AC GENERATOR
MOBILE
AC
GENERATORS
1.2 Liter, Liquid-Cooled
Gas/Gasoline Engine Models
Part 1
THE
AC
SECTION
1.1
1.2
1.3
1.4
1.5
1.6
TABLE OF CONTENTS
TITLE
How Generators Produce Electricity
Major Generator Components
Insulation Resistance Tests
Introduction to Troubleshooting
Troubleshooting Flow Chart
Troubleshooting Test Procedure
GENERATOR
NP and IM Series
RECREATIONAL
VEHICLE &
INDUSTRIAL
MOBILE
AC GENERATORS
Liquid Cooled 1.2 Liter
Gas Engine Models
Manual Familiarization
This Service Manual has baan dividad Into alevant (11) PARTS.'
Each PART consists of ons or mors SECTIONS. Each SECTION
Is divided Into two or more SUBSECTIONS. Each SUBSECTION
may be made up of one or more PARAGRAPHS.
A DIVIDER page separates each PART of the Manual. The
DIVIDER page provides a TABLE OF CONTENTS which lists the
SECTIONS that may be found In that PART.
Page numbers at the bottom of each page Identify the PART
number, SECTION number, and the specific page. For example.
Page 2.3-4 Indicates PART 2, SECTION 2 J, and Page 4 of that
SECTION. This type of numbering system allows Individual SEC
TIONS to be kept current without affecting page numbers In the
entire Manual.
Section 1.1- HOW GENERATORS PRODUCE ELECTRICITY
It has long been №own that a relationship exists between
Magnetic Induction
magnetism and electricity. Revolving field AC generators
depend on this relationship for their operation. If generator
problems are to be properly diagnosed, the service techriician
must understand this relationship. Magnetism can be used to
create an electrical voltage in a conductor. Conversely, elec
trical current flow through a conductor will create a magnetic
field around that conductor.
See Figure 1, below. When a conductor is moved
through a magnetic field, an electromotive force (EMF or
voltage) is induced Into the conductor. Movement of the
magnetic field so that It cuts across the conductor will also
create a voltage In the conductor. If the ends of the conductor
are connected to form a complete circuit, current will flow
through the conductor. The direction in which the current
flows depends on the polarity of the magnetic field and the
direction in which the magnetic field (or conductor) is moved.
The amount of voltage Induced into the conductor depends
on the strength or concentration of the magnetic field, i.e., the
stronger the magnetic field, the higher the induced voltage.
See Rgure 2. When current flows through a conductor,
a magnetic field is created around that conductor. The
strength of the magnetic field depends on (a) the amount of
current flow, (b) the number of turns or loops in the conductor.
The polarity of the magnetic field depends on the direction of
current flow through the wire. The following facts should be
evident:
□ If current flow through a conductor can be regulated, the
strength of the magnetic field around the conductor can
be regulated.
D If the strength of a magnetic field can be regulated, the
amount of voltage induced into a conductor by such a
magnetic field can also be regulated.
Figure 3 represents a simple AC generator, in which the
A Simple AC Generator
rotating magnetic field (Rotor) Is a permanent magnet. As the
magnet rotates, its magnetic field cuts across a stationary coil
of wires called a STATOR. When the magnet’s North mag
netic pole moves past the stator windings, current moves
through the wire in one direction. As the South magnetic pole
of the magnet passes the stator wires, current reverses itself
and moves through the stator in the opposite direction.
in the simple generator shown, the strength of the mag
net is fixed. That \ the magnetic field strength cannot be
changed since a permanent magnet is used. Because the
magnetic field strength is fixed, the voltage induced into the
stator coil is constant
If some method of regulating the magnetic field strength
of the magnetic could be found, the voltage induced into the
stator coil could be regulated as well.
Figure 3. A Simple Revolving Field Generator
Paga 1.1-1
A More Sophisticated Generator
Figure 4 Is a diagram of a more sophisticated generator.
A regulated direct current (DC) is delivered to the rotating
magnet (Rotor), via CARBON BRUSHES and SUP RINGS.
This creates a regulated magnetic field around the Rotor
which cuts across the stationary Stator windings to Induce a
regulated voltage into those windings. When the Stator circuit
is corfipleted by connecting a load, current will flow through
the Stator windings to the load.
Rgure 5, below, Is an operating diagram of a typical AC
A Typical AC Generator
generator. Operation of this typical generator may be briefly
described as follows:
D The ROTOR is attached to the engine’s power takeoff
(PTO) shaft and turns at the same speed as the engine.
D As the ROTOR turns, its magnetic field cuts across the
stationary coils of a STATOR EXCITATION WINDING
and dual STATOR AC POWER WINDINGS. A voltage is
induced into these stationary widings.
□ Unregulated alternating current (AC) is delivered from
the STATOR EXCITATION WINDING to the VOLTAGE
REGULATOR, via an EXCITATION CIRCUIT
BREAKER.
n "Sensing" leads deliver a signal of ACTUAL AC POWER
WINDING voltage to the VOLTAGE REGULATOR.
n The VOLTAGE REGULATOR electronically compares
the ACTUAL AC POWER WINDING voltage to a preset
REFERENCE VOLTAGE and changes №e STATOR
EXCITATION WINDING output to direct current (DC).
□ If ACTUAL POWER WINDING voltage Is less than the
REGULATOR’S preset REFERENCE voltage, REGU
LATOR action will increase direct current flow to the
ROTOR windings. The ROTOR magnetic field strength
will then increase and the voltage induced into the STA
TOR AC POWER WINDINGS will then increase.
□ When ACTUAL POWER WINDING voltage is greater
than the REGULATOR’S preset REFERENCE voltage,
direct current flow to the ROTOR will be decreased by
REGULATOR action to reduce ROTOR magnetic field
strength.
12
-S-
Rgure 5. Operating Diagram of a Typical AC Generator
ITEM
i
2
3
4
5
6
7 SLIP RINGS
11
4^
8
9
10
11
12
13
14
DESCRIPTION
RÓTOF1
STATOR POWER WINDING
STATOR EXCITATION WINDING
FIELD BOOST
ENGINE
BRUSHES
VOLTAGE REGULATOR
SENSING LEADS
THERMAL PROTECTOR
THERMAL PROTECTOR BYPASS
EXCITATION CIRCUIT BREAKER
ELECTRICAL LOAD
MAGNETIC FIELD
Page 1.1-2
□ The VOLTAGE REGULATOR will continue to increase
or decrease direct current flow to the ROTOR, In an
attempt to maintain STATOR AC POWER WINDING
voltage at the same value as the REGULATOR’S preset
REFERENCE voltage.
□ When the STATOR AC POWER WINDING circuit is
completed by connecting a load to the winding's AC
output leads, current will flow through the windings and
to the load.
Rotor Residual Magnetism
The Rotor may be considered a permanent magnet since
some residual magnetism is always normally present In the
Rotor windings. As a general rule. Rotor residual magnetism
atone (without regulated excitation current and without field
boost current) will produce a STATOR AC POWER WINDING
output of approximately 2 to 7 volts.
Field Boost
When the engine Is being cranked, direct current is
delivered to the Rotor windings from a source other than the
Stator excitation windings and Voltage Regulator. This direct
current, in effect, Hashes the field" every time the engine is
cranked. By applying field boost current to the Rotor during
cranking, an early "pickup" voltage Is induced into the Stator
windings to turn the Regulator on sooner and provide AC
output more quickly.
Failure of the field boost circuit rrray or may not result In
toss or dropout of AC power winding output voltage, depend
ing on the characteristics of the Individual generator. The
following general rules apply:
D If Rotor residual magnetism atone (without field boost) is
sufficient to turn the Voltage Regulator on and provide
the required pickup voltage, the generator will operate
normally with normal AC output voltage.
G If Rotor residual magnetism atone (without field boost) Is
NOT sufficient to turn the Regulator on and provide the
needed pickup voltage, generator AC output voltage will
not build and will be commensurate with Rotor residual
magnetism (about 2 to 7 volts AC).
G If regulated excitation current to the Rotor is lost. Stator
AC power winding output voltage will drop to a value that
is commensurate with Rotor residual magnetism (2 to 7
volts AC). The magnetic field strength created by field
boost current cannot be considered since it is available
only while cranking.
Figure 6. Field Boost Circuit (Gasoline Fuel System)
STARTER
CONTACTOR
-TO STARTER
§
11 CHOKE
* MODULE
° 1 FROM
*
TO ROTOR •
Figure 7. Field Boost Circuit (LP Gas Fuel System)
BATTERY
-Q)
ENGINE CONTROL
CIRCUIT BOARD
La/v-J
RESISTOR
47 OHM. 2 WATT
TO IGNITION COIL
9 RESISTOR ^9°^
9
-----
W\ T-
9
too OHM 200V.
1 WATT 1 WATT
W-
ENGINE CONTROL
CIRCUIT BOARD
DIODE
AMPY 1 AMf
TO
ROTOR
#
UNITS WITH GASOLINE FUEL SYSTEM;
See Figure 6. Units equipped with a gasoline fuel system
use a choke module (CM) which closes and opens a choke
solenoid (CS) during engine cranking to open and close the
carburetor choke.
UNITS WITH LP GAS FUEL SYSTEM:
Units equipped with a gaseous fuel system do not require
a carburetor choke and do not have a choke module. The field
boost circuit for such units Is shown in Rgure 7. While
cranking, battery voltage is delivered to Terminal No. 8 of an
engine control circuit board, to Wire No. 9, a field boost
assembly. Wire No. 4, and to the Rotor via brushes and slip
rings.
The field boost assembly, shown In Figure 8, consists of
a 100 ohm, 1 watt resistor (1^) and a 200 volt, 1 amp diode
(D2). The diode ensures that current will flow in one direction
only in the circuit. The resistor reduces the battery voltage
(12 volts DC) to approximately 9-10 volts DC.
GENERAL:
The excitation system is shown schematically in Figure
9. During operation, unregulated AC current from the Stator
excitation winding is delivered to the Voltage Regulator via a
Thermal Protector, Wires 2 and 6, an excitation circuit
breaker (CB4), and Wires 2A and 6. The Voltage Regulator
rectifies and regulates the current flow, which is then deliv
ered to the Rotor windings via Wires 4 and 1, and the brushes
and slip rings. Major components of the excitation system
include the following;
D Stator Excitation (DPE) Winding,
n Thermal Protector (TP).
D Excitation Circuit Breaker (CB4).
D AC Voltage Regulator.
D Brushes and Slip Rings,
n Rotor Assembly.
Excitation System
THERMAL PROTECTOR:
A Thermal Protector (tP) is physically imbedded in the
wire windings of the Stator assembly and electrically con
nected in series with the excitation winding AC output leads
to the Voltage Regulator. The device is a normally-closed (N.
C.), temperature sensitive switch. Should Stator tempera
tures exceed a preset level, the switch contacts will open. The
switch is self-resetting. That is, its contacts will close when
Stator temperatures decrease below a safe, preset level.
If the switch contacts open, excitation winding output to
the Regulator will terminate and the Regulator will shut down.
Generator AC output voltage will then drop to a value com
mensurate with the Rotor’s residual magnetism (about 2 to 7
volts AC).
The thermal protector is NOT accessible and cannot be
replaced. If it has failed open, it can be bypassed by connect
ing excitation lead No. 2 to a bypass lead No. 5. Once the
switch has been bypassed, overtemperature protection is no
longer available.
EXCITATION CIRCUIT BREAKER (CB4):
If this circuit breaker has failed open, the results will be
the same as a Thermal protector that has failed open. That
is, generator AC output will drop to about 2-7 volts AC
(residual).
Page 1.1-4
AC VOLTAGE REGULATOR:
See Figure 12. Sensing leads deliver ACTUAL AC power
winding voltage signals to me Regulator via Leads 11 and 22
and Regulator terminals 5 and 6. The Regulator electronically
compares this ACTUAL signal to a preset REFERENCE
voltage, then acts to maintain an ACTUAL voltage that Is
equal to the REFERENCE voltage.
If ACTUAL voltage is less than the preset REFERENCE
voltage, the Reoulator will increase excitation current flow to
the Rotor. The Rotor's magnetic field will then strengthen and
the AC output voltage will increase.
If ACTUAL voltage is greater than preset REFERENCE
voltage. Regulator action will decrease excitation current flow
to the Rotor. The Rotor’s magnetic field strength will drop and
ACTUAL voltage will decrease.
The typical AC Voltage Regulator shown in Figure 12 has
a single amustable potentiometer, used to establish the de
sired REFERENCE voltage.
BRUSHES AND SLIP RINGS:
The Brushes and Slip Rings (Figure 13) allow excitation
current flow to be transmitted rrom a stationary member to a
rotating member. The Slip Rings are actually a part of the
Rotor assembly. As a general rule, the positive slip ring is the
one nearest the Rotor bearing. Wire No. 4 is the positive
brush lead; Wire No. 1 is the negative baish lead.
NOTE: At the time thie Manual was written, all NP/IM
Series generators were equipped with the dual, 1-phasa
stator configuration. Some other possible stator config
urations will be mentioned here to cover future possibil
ities.
Stator AC Power Connection Systems
GENERAL:
Any one of several different connection systems are
used on NP and IM Series generators. Theses are(a) dual
1-phase, (b) 3-phase Delta, and (c) 3-phase Wye-Connected
systems.
DUAL WINDING. 1-PHASE SYSTEM:
Figure 14 is a schematic representation of dual 1-phase
Stator AC power windings. Each Stator winding can supply a
120 volts AC output. When the two windings are connected
In series to form a 3-wire connection system, a 240 volts AC
output results.
Connected for Dual Voltage Output Some dual wind
ing systems may have been connected to provide a dual
voltage output (120 and/or 240 volts AC). See Figure 15.
Stator AC output leads 11 (T1) and 44 (T3) form the two hot
leads. The Junction of Stator leads 22 and 33 form the
"Neutral’ line (T2).
Connected for Single Voltage Output: If desired, the
Stator AC ou^ut leads can be reconnected for single voltage
output only (Figure 16). When this Is done, a jumper wire must
be connected between the two main circuit breakers (CB1
and CB2).
Page 1.1-5
stator AC Power Connection Systems (Continued)
3-PHASE DELTA STATOR SYSTEM:
Figure 17 is a schematic representation of a 3-phase
Delta Stator configuration. Phase rotation is L1-L2-L3. The
“Neutral" line is designated “LO".
3-PH^ASE WYE-CONNECTED SYSTEM:
See Figure 18. This type of Stator consists of six (6) coils
and twelve (12) leads coming out of the Stator. The twelve
leads are reconnectable to supply several different voltages.
Page 1.1-6
Section 1.2- MAJOR GENERATOR COMPONENTS
This section will discuss generator disassembly, Inspec
tion of components, and reassembly. See Figure 21 on Page
1.2-2.
Generator Disassembly
To disassemble the generator, proceed as follows. See
Figure 21.
1. Remove the four capscrews, lockwashers and flatwashers
(Items 22, 23 and 24) that retain the REAR BEARING CAR
RIER PLATE (Item 20) to the REAR BEARING CARRIER
(Item 15). Remove the REAR BEARING CARRIER PLATE
(Item 20).
2. Remove the Rear Bearing Carrier GASKET (Item 18).
3. Disconnect wires from BRUSH HOLDERS (Item 16).
4. Remove SCREWS (Item 17) that retain the BRUSH HOLD
ERS (Item 16) to the Rear Bearing CARRIER (Item 15).
Remove the BRUSH HOLDERS (Item 16).
5. Remove hardware that retains the Rear Bearing CARRIER
(Item 15) to the generator mounting base.
6. Remove the four long CAPSCREWS (Item 21), along with
four LOCKWASHERS (Item 10).
7. A REAR BEARING CARRIER PULLER tool Is available.
See Figure 19. To order the tool, specify Part No. 74078.
a. Retain the PULLER TOOL to the Rear Bearing CAR
RIER (Item 15) using the same M6-1.00 x 8mm screws
ltem 22) that were used to retain the Rear Bearing Carrier
»LATE (Item 20).
i
b. Turn the center bolt on the PULLER TOOL (Figure 19)
clockwise until the Rear Bearing CARRIER (Item 15) is
free of the Rotor bearing.
c. Completely remove the Rear Bearing CARRIER (Item
' 15).
8. Free the STATOR ASSEMBLY (Item 14) from the
BLOWER HOUSING (Item 2). Completely remove the STA
TOR ASSEMBLY (Item 14).
Introduction
12. Remove the ROTOR ASSEMBLY (Kern 1) with the FAN
& RING GEAR (Item 25) attached.
13. Remove CAPSCREWS and LOCKWASHERS (Items 34
and 36) that retain the FLEX PLATE (Item 28) to the engine
flywheel. Remove the FLEX PLATE (Item 28).
14. If the FAN & RING GEAR is to be removed from the
ROTOR (Item 1), proceed as follows:
a. Remove CAPSCREW and LOCKWASHER (Items 30
and 31) that retain the FAN & RING GEAR to the ROTOR.
b. Remove the SPACER (Item 27).
c. Remove the FAN & RING GEAR (Item 25) from the
ROTOR.
NOTE: The FAN & RING GEAR ASSEMBLY (Item 25) Is
retained to the ROTOR shaft by a KEY (Item 26).
Inspection of Major Components
REAR BEARING CARRIER Pj^TE:
Air slots in the Rear Bearing Carrier Plate allow cooling
air to be drawn into the generator by fan action during
operation. These air slots must be kept open and unob
structed. Clean the plate and check for cracks, obvious
damage. Replace the Plate, If necessary.
BRUSHES:
Inspect both Brush Holders and their Brushes. Look for
cracks, chipping, excessive wear. Replace any damaged
Brush Holder. Brushes should be replaced as a complete set.
Inspect Boish Leads No. 1 and 4, replace any damaged or
defective Brush Lead.
Figure 20. Brush Holders, Brushes and Leads
I
9. Remove the hardware that retains the STARTER (Item 40)
to the ENGINE PLATE (Item 29). Remove the STARTER.
10. Remove all fasteners that retain the BLOWER HOUSING
(Item 2). Remove the BLOWER HOUSING.
11. Remove CAPSCREWS (Item 33) that retain the FLEX
PLATE (Item 28) to the FAN & RING GEAR (Item 25).
-
+'
BRUSH WITH RED
LEAD CLOSEST
BRUSH
TO ROTOR BEARING
HOLDER
SCREW
n-rf
REAR BEARING CARRIER:
The Rear Bearing Carrier is an aluminum casting. Clean
the casting and blow dry with compressed air. Inspect care
fully for cracks, damage. An insert is pressed into the bearing
carrier center bore, to accept the Rotor bearing. Use an Inside
micrometer to check the diameter of the Insert. Replace the
Rear Bearing Carrier If its insert’s inside diameter (I.D.) is not
within the following limits:
2.384-2.386 Inches (71.996-72.012mm)
Page 1.2-1
Figure 21. Exploded View of AC Generator Assembly
ITEM
1 1
2 1
3
4 5
5 5
6
7
8
9
10 9
11 3
12 2
13*
14 1
15
16 2
17
18
19
20
21
22
23
24 4
25
26
* User
QTY
i to mount the generator control panel. ** Part of Engine Governor system.. See Part 7.
DESCRIPTION ITEM QTY DESCRIPTION
Rotor Assembly 27
Blower Housing
1
4
1
1
2
4
1
4
1
1
1
4
4
8
1
1
Air Outlet Screen 29 1
Pan Head Machine Screw 30 1
Lockwasher
Flatwasher 32
Hex Head Capscrew 33 4
Hex Head Capscrew
Flatwasher
Lockwasher 36
Hex Nut
Dowel Sleeve
Vibration Dampener 39 3
Stator Assembly
Rear Bearing Carrier 41 1
Brush Holder
Hex Head Screw 43 1
Rear Bearing Carrier Gasket
Flame Arrestor
Rear Bearing Carrier Plate
Hex Head Capscrew
Hex Head Capscrew
Lockwasher 51
Flatwasher
Rywheel & Ring Gear Assembly
3/8* square x 1" Key
28 1
31
34
35 7
37 1
38 1
40
42
44
45
46
47- 1
50 1
52
12
1
1
4
5
1
2
1
1
1
1
4
Magnetic Pickup Assembly
Spacer
Flex Plate
Engine Plate
Hex Head Capscrew
Lockwasher
Hex Head Capscrew
Hex Head Capscrew
Lockwasher
Hex Nut
Hex Head Capscrew
Hex Head Capscrew
Hex Nut
Flatwasher
Starter Motor
Starter Adapter
Hex Head Capscrew
Fan Access Cover
Ignition Coll
Ignition Coll Bracket
Screw
Rubber Grommet
Hex Head Capscrew
Hex Nut
Page 1.2-2
STATOR ASSEMBLY;
Clean the Stator can exterior surfaces with a soft brush
or cloth. Use clean, dry, low pressure air (25 psi maximum)
to clean the Stator.
Use an ohmmeter or a volt-ohm-milliammeter (VOM) to
test the resistance of Stator AC power windings and excita
tion (DPE) windings. See Section 1.6.
Use an insulation resistance tester (megohmmeter or
hi-pot tester) to check the condition of stator insulation (see
Section 1.3). If stator insulation is breaking down, dry the
stator by blowing warm, dry air across it for several hours. Do
NOT exceed 185* F. (85‘ C.). If insulation resistance Is still
low after drying, replace the stator assembly.
BLOWER HOUSING:
Clean the cast aluminum blower housing. Inspect the
housing carefully for cracks, damage.
FLEX PLATE;
The flex plate is of 16 gauge steel. Clean the flex plate,
then inspect it carefully for cracks, damage, wear. Check all
holes for elongation and wear.
ROTOR ASSEMBLY;
Use clean, dry, low pressure air (25 psI maximum) to
clean the rotor. Use a volt-ohm-mllliammeter ^OM) to check
the resistance of Rotor windings (Section 1.6).
Check the Rotor bearing for binding, seizing, roughness.
The bearing is pre-lubricated and sealed; It requires no addi
tional lubrication for the life of the bearing. If the bearing Is
defective, replace the Rotor assembly.
Check the keyway in the Rotor’s tapered shaft for wear
or damage. Also, inspect the drive key.
Inspect the slip rings. A dull or tarnished appearance
indicates oxidation on the slip ring surface. If necessary,
clean the slip rings with fine sandpaper. DO NOT USE ANY
METALLIC GRIT TO CLEAN SLIP RINGS.
Use an Insulation resistance tester (megohmmeter or
hi-pot tester) to check fhe Rotor for Insulation breakdown. If
insulation resistance Is low, dry the Rotor with heated, dry air.
DO NOT EXCEED 165* F. (85 C.). If the insulation resistance
is still low after drying, replace the Rotor assembly.
FAN AND RING GEAR ASSEMBLY:
During factory assembly, the ring gear is heated to 400*
F. and the blower fan is installed. The entire assembly is then
statically balanced. If the fan and ring gear must be replaced,
replace It as an assembly.
Page 1.2-3
Section 1.3- INSULATION RESISTANCE TESTS
Effects of Moisture and Dirt
The insulation in RV and IM generators is moisture
resistant. However, prolonged exposure to moisture will grad
ually decrease the resistance of Stator and Rotor insulation.
If moisture is allowed to remain in contact with generator
windings, some of the moisture will be retained in cracks and
voids of the iunsulation. This will result in a reduced insulation
resistance and, eventually, the unit’s AC output will be af
fected.
Dirt can make the problem worse since it tends to hold
the moisture Into contact with the windings.
Salt, as from sea air, can also worsen the problem since
salt absorbs moisture from the air. When salt and moisture
combine, they make a good electrical conductor.
Because of the detrimental effects of dirt and moisture,
the generator should be kept as clean and dry as possible.
Stator and Rotor windings should be tested periodically with
an insulation resistance tester such as a megohmmeter or
hi-pot tester. If the insulation resistance is excessively low,
drying may be required to remove moisture. After drying, a
second test of the Insulation should be performed. If resis
tance Is still low after drying, replacement of the defective
windings may be necessary.
Insulation Resistance Testers
Figure 22 shows Just one type of hi-pot tester. The tester
shown is one of many brands that are commercially available.
It has a "Breakdown^ lamp which will glow to Indicate insula
tion breakdown during the test.
Normally, the resistance of insulation is measured on the
order of millions of ohms, it can be measured w'rth a device
called a 'megger', which is a megohm meter (meg is for
million) and a power supply. The power supply voltage varies
but the most common Is 500 volts. A megger voltage over 500
is NOT recommended.
When using a hi-pot tester or megger to measure Insu
lation resistance, be sure to follow the manufacturer's instruc
tions carefully.
CAUTION: Before attempting to measure Insula
tion resistance In any winding, first disconnect
any electronic components, regulators, diodes,
surge protectors, protective relays, etc., from the
circuit. Such components will be destroyed by the
high voltages generated by a megger or hl-pot
tester.
To measure Insulation resistance, connect one tester
lead to the leads for the winding to be tested and the other
tester lead to the generator frame. Make sure no leads of the
part being tested are touching any metal parts of the gener
ator. If the 'Neutral' is grounded, it must be disconnected.
Follow the tester manufacturer’s instructions and perform the
resistance test.
Insulation Resistance- Main Stator
All stator leads (No. 11, 22, 33, 44, 2 and 6) must be
Isolated from ground and connected together. Connect one
hi-pot or megger test lead to the main stator leads. Connect
the other hi-pot or megger lead to the generator grounding
stud. Set the hi-pot tester or megger voltage to '500'. Follow
the tester manufacturer’s Instructions and take the reading.
Do not apply the voltage for longer than one (1) second.
If a hi-pot tester like the one shown in Figure 22 is being
used, a 'Breakdown' lamp on the tester will glow during the
one second test to indicate an Insulation breakdown.
If a megger is used to perform the test, the minimum
acceptable value can be calculated using the following for
mula:
Minimum Insulation в
Resistance (Megohms)
Example: For a generator rated 240 volts AC:
2^+1b 1.24 Megohms
Generator Voltage +1
-------------TOOO
------
1000
H the reading Is below the recommended value, the
winding must be dried out
Rotor insuiation Resistance
Before testing Rotor insulation, гтшке sure the Rotor Is
completely Isolated. This can be done by removing both
brush holders with their brushes.
Connect one hi-pot tester or megger lead to the positive
Rotor slip ring, the other test lead to a clean frame ground
(such as the Rotor shaft). Set the tester to '500' volts and
apply voltage - DO NOT APPLY VOLTAGE LONGER THAN
ONE SECOND.
If a hi-pot tester is used. Its 'Breakdown' lamp will come
on to Indicate an insulation breakdown.
If a megger Is used, the minimum acceptable value Is 1.5
megohms. ,
If insulation Is breaking down under the applied voltage,
the Rotor must be dried out. After drying, retest the Rotor. If
insulation still breaks down after drying, replace the Rotor
assembly.
Greasy dirt or dirt that Is caked may be loosened with a
soft brush or a clean, damp cloth. A vacuum system may be
used to clean up loosened dirt. Loose dust and dirt may also
be blown away with clean, dry, low pressure air (25 psi
maximum).
Drying the Generator
To dry the generator without disassembling it, proceed
as follows:
1. Open the generator’s main circuit breaker. NO ELECTRI
CAL LOADS MUST BE APPLIED TO THE UNIT WHILE
DRYING.
Page 1.3-1
Cleaning the Generator
Drying the Generator (Continued)
2. Disconnect Wires No. 4 from the Voltage Regulator.
3. Provide an external source to blow warm, dry air through
the generator. DO NOT EXCEED 185* F. (85* C.).
4. Start the generator and iet it run for 2 or 3 hours.
5. Stop the engine and retest Stator and Rotor insulation for
breakdown.
Page 1.3-2
Section 1.4- INTRODUCTION TO TROUBLESHOOTING
A revolving field RV/IM type generator does not have a
Introduction
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
required if one Is to achieve effective troubleshooting and
repair. The technician must understand why generators be
have or don’t behave as they should. This section is Intended
to introduce the service technician to some of the fundamen
tals of troubleshooting generator problems.
DANGER: RV AND IM TYPE GENERATORS PRO
DUCE EXTREMELY HIGH AND DANGEROUS
VOLTAGES. CONTACT WITH LIVE WIRES AND
TERMINALS MAY RESULT IN HAZARDOUS AND
POSSIBLY FATAL ELECTRICAL SHOCK. ONLY
PERSONNEL WHO HAVE BEEN TRAINED IN THE
SERVICING AND REPAIR OF RV/IM GENERA
TORS SHOULD ATTEMPT TO TROUBLESHOOT,
TEST OR REPAIR SUCH EQUIPMENT.
Tools and 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 be equipped with wrenches in
both english and metric sizes. A selection of nut drivers
(english and metric) is also recommended. In addition to
common hand tools, the following specialized equipment
should be available;
Figure 24. A Typical Frequency Meter
1. Volt-Ohm-Milliammeter or VOM
a. An accurate VOM Is necessary fortesting, adjusting and
troubleshooting.
b. Simply having a VOM is not enough- the technician must
be familiar with electrical circuits, must be able to read
wiring diagrams and electrical schematics, and must be
able to use the VOM effectively.
C. An accurate digital type VOM is recommended.
2. Frequency Meter
a. Frequency meter reads alternating current (AC) fre
quency, in HERTZ or CYCLES PER SECOND.
b. Generator AC output frequency must be known in order
to check and adjust engine-generator operating speed.
See "ROTOR ROTATIONAL SPEECt in this section.
3. Insulation Resistance Tester
a. See Section 1.3, ‘INSULATION RESISTANCE TESTS".
b. This tester will allow the user to test Rotor and Stator
Insulation for breakdown under an applied voltage.
4. Load Bank- will permit a known electrical load to be applied
to the generator, i.e., fortesting and adjustment of the gener
ator under load.
Rotor Rotational Speed
The revolving field (Rotor) is directly connected to the
engine crankshaft and will rotate at the same speed as the
engine. Engine speed is held nearly constant by an engine
governor. Some generator models utilize a constant speed,
MECHANICAL governor; other models may be equipped with
an ELECTRONIC governor. See Part 7, "ENGINE SPEED
CONTROL SYST^Kr.
Generators may be equipped with either a 2-pole or a
4-pole Rotor. A 2-poie Rotor has a single North magnetic pole
and a single South magnetic pole. A 4-pole Rotor has two
North magnetic poles and two South magnetic poles. The
following apply to 2 and 4-pole Rotor assemblies:
A. 2-Pole
Figure 25. Typical 2 and 4-Pole Rotors
B. 4-Pole
Page 1.4-1
Rotor Rotational Speed (Continued)
1. A 4-Pole Rotor must be operated at 1800 rpm to supply a
60 Hertz AC output frequency: or at 1500 rpm for a 50 Hertz
AC output frequency.
2. A 2-pole Rotor must be operated at 3600 rpm for a 60 Hertz
AC output frequency: or at 3000 rpm for a 50 Hertz frequency.
The following formulas apply to (a) frequency, (b) rpm, and
(c) number of Rotor poles:
FREQUENCY = RPM X NO. OF ROTOR POLES
2x60
RPM o
NO. OF ROTO№ 2 X 60 X FREQUENCY
POLES RPM
2 X 60 X FREQUENCY
NO. OF ROTOR POLES
Relationship of Voltage & Frequency
The generator’s AC voltage regulator mounts a single
adjustable potentiometer, used for adjustment of tne
Regulator’s REFERENCE voltage (see ’EXCITATION S/S-
TEAf on Page 1.1-4). The potentiometer is called simly a
'Voltage Adjust Potentiometer* and is adjusted with the gen
erator running at no-load and at a specific operating speed.
It is important that the engine speed governor be properly
adjusted before the Voltage Adjust Potentiometer setting is
attempted. The no-load AC frequency and voltage settings
should be as follows:
1. Shut the generator engine down.
2. Connect a voltmeter to the generator’s AC output
leads.
3. Disconnect Wires No. 4 and 1 from the Voltage Reg
ulator.
4. Connect a jumper wire from terminal #1 (Wire #15) of
the engine control circuit board to the terminal end of Wire #4
(just disconnected from the Reguiator).
5. Connect a jumper wire from terminal #2 of the engine
control circuit board (Wire #0, ground) and to the terminal end
of Wire #1 Gust disconnected from the Regulator).
6. Start the generator and let It run at no-load (main
breakers open) and at its rated speed.
7. Read the generator’s AC output voltage from the
voltmeter connected In Step 2. Reading should be approxi
mately one-half rated voltage (about 40-60 volts line-to-neutral or 80-120 volts line-to-line).
8. Shut the generator down.
9. Reconnect Wires No. 1 and 4 to the Voltage Regulator.
If voltage reading is normal in Step 7, the Wires #1 and
4 circuit, brushes and slip rings. Rotor and Stator are working
satisfactorily. The problem is In the circuit that Includes (a)
stator excitation windings, (b) thermal protector, (c)excitation
circuit breaker (CB4), (d) Wires 2 and 6, and (e) Voltage
Regulator.
NOTE: Field boost current la available to the Rotor only
while the engine Is cranking. Loss of excitation current
flow to the Rotor will result In a decrease In generator AC
output voltage to a value commensurate with Rotor re
sidual magnetism (about 2 to 7 volts AC),
1. For Units Rated 120/240 Volts at 60 Hertz: Set AC
frequency to 60.5-63.5 Hertz and Voltage to 121-127 volts
AC (line-to-neutral), or 242-254 volts AC (line-to-line).
2. For units rated 110/220 volts at 50 Hertz: Set AC fre
quency to 49-52 Hertz and voltage to 108-112 volts (line-toneutral).
Visuai inspection
Quite often problems that occur in the generator can be
detected by making a thorough visual inspection. Remove
covers and look for any obvious problems. Burned windings,
broken connections, leads, mounting brackets, etc., can usu
ally be Identified. Also look for loose or frayed insulation,
loose or dirty electrical connections, broken wires.
Verify that the generator AC output leads are properly
connected for (a) single voltage outpiut, or (b) dual voltage
output. See 'STATOR AC POWER CONNECTION SV%-
TEMSr on Page 1.1-5.
Check for any foreign objects, loose nuts, bolts, and
electrical connectors. Clear away paper, leaves, snow, build
ing materials, etc., that might be sucked into the generator.
Constant Excitation Test
The generator’s AC output voltage will vary with Rotor
speed, generator design, connected loads, and excitation
current to the Rotor, if the generator speed and excitation
cunenttothe Rotor are known, the no-load AC output voltage
can be measured and compared to the design value. A
problem can be isolated to (a) Stator Excitation (OPE) wind
ings to Voltage Regulator circuit, including the Regulator, or
(b) Voltage Regulator to Rotor circuit, excluding the Regula
tor, or (c) the Stator assembly. Perform the test as follows:
a DC or AC voltage.
The DC voltage most often measured will be battery
voltage (12 volts DC).
When measuring AC voltages, the generator will have to
be running at rated speed and may have some of the protec
tive guárete and covers removed. BE CAREFUL. It is best to
shut the unit down when connecting meters. Use the meter’s
instruction manual to verify its operation and limitations.
Page 1.4-2
Alternating current measurements can be taken with a
Measuring Current
'clamp-on* type ammeter. Amperage should never exceed
the nameplate rating when running the intended electrical
load(s).
Resistance of the main stator windings is very low. Some
meters are not able to read such a low resistance and, for that
reason, use of a very sensitive digital type meter is recom
mended. A standanj VOM can be used to check for continuity,
shorts or grounded condition.
Effects of Engine Power
The generator engine must provide adequate power to
operate the generator at rated load. The greater the load
current (amperage) or load watts, the greater the engine
power that is needed. As a general rule, approximately 2
engine horsepower is needed for each 1000 watts (1.0 kW)
of generator power.
If the generator’s wattage/amperage capacity is ex
ceeded, engine power may not be sufficient to handle the
Increased load. The result will be a decrease in engine speed
(rpm) and a corresponding reduction int AC output frequency
and voltage.
A badly worn engine, one that has lost compression, or
one with a mechanical problem may not be able to handle a
load within the generator’s rated capacity. Problems with
generator AC output are often the direct result of an engine
problem, rather than a generator problem.
If engine speed, AC frequency and voltage are normal
when the generator Is running aty no load, but deteriorate
when electrical loads are applied, an underpowered engine
may be the cause of the problem.
Measuring Resistance
Page 1.4-3
Section 1.5- TROUBLESHOOTING FLOW CHART
TEST 1-CHECK NO-LOAD
VOLTAGE AND FREQUENCY
VOLTAGE &
FREQUENCY
BOTH GOOD
VOLTAGE &
FREQUENCY
BOTH HIGH
IVQEVOLTAGE LOW,
FREQUENCY
GOOD
VOLTAGE
AND
FREQUENCY
Page 1.5-1
Using the Troubleshooting Flow Chart
When a problem occurs with an RV/IM series generator
set, the first step is to determine exactiy what that problem is.
The nature of the problem can usually be found by checking
the unit’s no-load AC output voltage and frequency. This is
Test 1 in the Flow Chart. A check of the no-load voltage and
frequency will usually end with one of the following results;
1. Voltage and frequency are both good. If this is the case,
the next step is to check voltage and frequency with electrical
load applied.
2. Voltage and frequency are both high or bw, usually an
engine governor problem, I.e., governed speed too high or
too low.
3. Voltage is low, but AC frequency is good. The cause of
this problem can often be found by perfomiing a "Fixed
Excitation" test
4. Voltage and frequency read "zero".
Once the nature of the problem is defined, the cause of
the problem can usually be found by following the explana
tions and arrows in the Flow Chart
Use the'TROUBLESHOOTING FLOWCHART in con
junction with test instructions in Section 1.6, 'TROUBLE
SHOOTING TEST PROCEDURES'.
r-\
Page 1.5-2
Section 1.6- TROUBLESHOOTING TEST PROCEDURES
The following numbered tests may be performed in con
Introduction
junction with identically numbered tests in the "TROUBLE
SHOOTING FLOW CHART (Section 1.5). The "FLOW
CHART* has been carefully planned to prevent guesswork
and to locate most common generator problems.
NOTE: Quite often the cause of a problem can be deter
mined by completing a close visual Inspection of the
generator. See "VISUAL INSPECTION" on Page 1.4-2.
Test 1> Check No-Load Voltage and Fre
quency
DISCUSSION:
When a generator problem occurs, the first step Is to
identify the problem. This can usually be accomplished
quickly by checking the no-load AC ouÿut voltage and fre
quency. Once the exact problem has been identified, the
cause of the problem can usually be isolated by continuing
orderly tests as shown in the "TROUBLESHOOTING FLOW
CHART".
NOTE: You will have to determine whether the AC leads
have been connected for single voltage output only (120
volts, 60 Hertz orilo volts, SO Hertz); or for dual voltage
output (120/240 volts, 60 Hertz or 110/220 volts, 50 Hertz).
See "STATOR AC POWER CONNECTION SYSTEMS" on
Page 1.1-5.
PROCEDURE:
1. Connect an AC voltmeter and AC frequency meter across
the generator’s AC output leads. Open main circuit breaker.
a. If connected for single voltage AC output, connect the
meters across leads T1 and 12.
b. If connected for dual voltage output, connect meters
across leads T1 and 12 or 12 and T3 for a 120 volts, 60
Hertz (or 110 volts, 50 hertz) reading. For a 240 volts, 60
Hertz (or 220 volts, 50 hertz) reading, connect meter test
leads across generator leads T1 andT3.
2. Start the generator engine, let It stabilize and wami up.
3. Read the AC output voltage and frequency. Readings
should be as follows:
a. For units rated 120/240 volts, 60 hertz; readings should
be 121 -126 volts at 61 -63 Hertz; or 242-252 volts at 61 -63
Hertz.
b. For units rated 110/220 volts, 50 hertz; readings should
be 111 -113 volts at 51 -53 Hertz; or 222-226 volts at 51 -53
Hertz.
RESULTS:
1. If the no-load voltage and frequency are good, go to Test
2.
2. If no-load voltage and frequency are both high or low, go
to Test 5.
3. If frequency reads good but voltage Is low, go to Test 6.
4. If voltage and frequency read "zero", go to Test 1.0.
Test 2- Check Load Voltage and Fre
quency
DISCUSSION:
Generator problems are sometimes caused by exceed
ing the wattage/amperage capacity of the unit. What appears
to be a generator problem may, in fact, be caused by an
engine that has lost power. The following facts apply:
D Quite often, the maximum wattage that can be supplied
by a generator Is limited by available engine power.
When connected loads exceed a critical point, engine
speed will droop. With a reduction in engine speed will
come a voltage and frequency loss.
O It is possible that an engine can lose power to the extent
that even normal rated generator output power can be
achieved. Engine speed, frequency and voltage can then
droop before a unit's rated maximum capacity has been
reached.
PROCEDURE:
If no-load AC output voltage and frequency were within
limits, but operational problems occur when electrical loads
are applied, check the output voltage and frequency under
load as follows:
1. Connect an AC voltmeter and frequency meter across the
generator’s AC output leads. Close the main circuit breaker.
2. Start the generator, let it stabilize and warm up.
3. Apply an electrical load to the generator equal to its rated
maximum wattage/amperage capacity.
4. Read the voltage and frequency.
a. Units rated 120/240 volts, 60 Hertz: Readings should
be at least 116 volts and 58 Hertz (or higher).
b. Units rated 110/220 Volts, 50 Hertz: Readings should
be at least 107 volts, 48 Hertz (or greater).
RESULTS:
1. If load voltage and frequency are below limits, go to Test
3.
2. If voltage and frequency are good, discontinue tests.
Test 3- Check Load Watts and Amperes
DISCUSSION:
If the unit's AC output frequency and voltage drop below
limits when electrical loading is applied, it is possible that the
rated capacity of the generator has been exceeded.
PROCEDURE:
Add up wattage ratings of all electrical loads applied to
the generator at one time. This total should not be greater
than the unit’s rated maximum wattage capacity. If desired, a
clamp-on ammeter may be used to measure load current. The
unit’s rated maximum amperage capacity should not be ex
ceeded.
Page 1.6-1
Test 3- Check Load Watts and Amperes
(Continued)
NOTE; The best way to check load wattage and amperage
la to use a load bank. A load bank will allow the operator
to apply a known wattage/amperage load to the generator
and win permit voltage, frequency and amperage to be
read directly from the load bank.
RESULTS;
1. If the generator Is overloaded, reduce the load to the unit’s
rated capacity.
a. If voltage and frequency are excessively low at the unit’s
rated capacity or less, go on to Test 4.
b. If voltage and frequency are acceptable at the unit’s
rated capacity, discontinue tests.
2. If the load Is within the unit’s rated capacity, but load
voltage and frequency are excessively low, go on to Test 4.
Test 4- Check Engine Power
DISCUSSION:
If excessive rpm and frequency droop occurs when
electrical loads are applied, the engine may be underpowered
due to a malfunction.
PROCEDURE:
Check the engine for (a) adequate air flow, (b) clogged
air cleaner, (c) incorrect timing, (d) mechanical failure, etc.
RESULTS:
1. If engine problems are found, repair the engine as neces
sary.
2. If engine checks good, go on to Test 5.
Test 5- Check & Adjust Engine Governor
DISCUSSION:
If engine speed (and frequency) droop excessively under
load, the engine governor may require adjustment
PROCEDURE:
Refer to Part 7, "ENGINESPEED CONTROL SYSTEM-.
Governor adjustment procedures for both the mechanical and
electronic type governors can be found in Part 7.
RESULTS:
1. It, after governor adjustment, voltage and frequency output
at no-load and under load are good, discontinue tests.
2. If, after governor adjustment, frequency Is good, but volt
age is excessively low, go on to Test 6.
Test 6- Do a Fixed Excitation Test
DISCUSSION:
See "CONSTANTEXCITATION TEST on Page 1.4-2.
PROCEDURE:
’TEST" on Page 1.4-2.
RESULTS:
1. If voltage is excessively low, go to Test 7.
2. If about 1/2 rated volts is indicated, go to Test 12.
Test 7- Check Wires 1 and 4
DISCUSSION:
the fixed or constant excitation test (Test 6) consisted
of applying battery direct current to the Rotor windings (12
volts DC). With the normal excitation circuit disconnected,
application of battery current should result In approximately
one-half rated voltage output (about 60-80 volts AC).
If batteiy current is applied and AC output voltage te
excessively low, a problem exists in Wires 1 and 4 from the
Regulator, or the brushes and slip rings, or the Rotor or stator
windings.
If the application of battery current results in an AC output
of about one-half rated volts, but AC output voltage is low
during normal operation, a problem exists in the stator exci
tation (DPE) windings, in the excitation circuit between the
stator DPE windings and the Regulator, or in the Regulator
itself.
PROCEDURE:
1. Visually inspect Wires 1 and 4, between the Voltage
Regulator and the brushes.
2. Use a VOM to test Wire 1 (between the brushes and
Regulator) for continuity.
3. Check Wire 4 (between the brushes and Regulator) for
continuity.
4. Check that Wires No. 1 and 4 are properly connected at
the Regulator and at the brushes.
RESULTS:
1. Repair, replace or reconnect wires 1 and 4 as necessary.
2. If Wires 1 and 4 are good, go to Test 8.
Test 8- Check Rotor
DISCUSSION:
Problems will be encountered if the Rotor Is (a) open, (b)
shorted, or (c) grounded. This test will determine If any of
these problems exist in the Rotor.
PROCEDURE:
1. If Rotor Is installed, remove the bearing carrier cover to
gain access to the Rotor brushes and slip rings.
2. Disconnedct Wires 1 and 4 from the brushes, to prevent
Interaction.
3. Connect the positive test lead of an ohmmeter to the
positive slip ring, the common test lead to the negative slip
ring. The positive slip ring Is the one nearest the Rotor bearing
(see Figure 28). The meter should indicate the resistance of
the Rotor windings, approximately 8.5 ohms (plus or minus
10%) for both 8 and 10 kW models.
4. Set a VOM to a very high resistance scale, such as
■Rxl 0,000" or "RxlK". Zero the meter. Connect the positive
VOM test lead to the positive slip ring. Connect the negative
VOM test lead to a clean frame ground, such as the Rotor
shaft. The meter should read "infinity".
RESULTS:
1. In Step 3, a very high resistance or "infinity" Indicates an
open or partially open condition. Replace the Rotor.
2. In Step 3, a very low resistance indicates a shorted or
groundea condition. Replace the Rotor.
3. In Step 4, any reading other than "infinity" Indicates a
groundea condition. Replace the Rotor.
4. If all Rotor readings are good, go to Test 9.
Page 1.6-2
Figure 28. Checking Rotor Resistance
Test 9> Check Brushes and Slip Rings
DISCUSSION:
if the fixed (constant) excitation test did not result in an
AC output voitage of approximateiy one-haif rated voits, one
possibie cause of the probiem might be defective brushes
and/or slip rings.
Test 10- Test Main Circuit Breaker
DISCUSSION:
■ If AC output voltage and frequency are "zero", one pos
sible cause of the problem is an open or failed main circuit
breaker.
PROCEDURE:
Make sure the main circuit breaker Is set to Its ’Closed’
position, if the breaker Is closed, check it for continuity.
RESULTS:
1. Replace main circuit breaker. If It Is defective.
2. If main breaker is good, go to Test 11.
Figure 30. Main Circuit Breaker (Typical)
PROCEDURE:
Remove Wires 1 and 4 from the brushes. Then, remove
the brush holders from the rear bearing carrier. Inspect the
brushes and brush holders. Replace, It cracked, damaged,
worn excessively, etc.
Inspect the slip rings. If they are dull or tarnished, they
can be cleaned with fine sandpaper. DO NOT USE ANY
METALLIC GRIT TO CLEAN SLIP RINGS. Use low pressure
air (25 psi or less) to blow away cleaning residue.
Reassemble brushes and brush holders to rear bearing
carrier. Make sure brushes are properly seated in brush
holders and are contacting the slip rings properly. Reconnect
Wires 1 and 4 to brushes. Rotate the Rotor several times to
seat the brushes against the slip rings.
RESULTS:
Clean slip rings, replace bad brushes or brush holder(s)
as necessary.
Test 11- Check AC Power Lead Connec
tions
DISCUSSION:
The stator's AC output leads must be property connected
as outlined under ‘STATOR AC POWER CONNECTION
SYSTEMSr (Page 1.1-5).
PROCEDURE:
Check that Stator AC output leads 11,22,33 and 44 (as
well as T1, T2 and T3) are property connected as shown In
the appropriate wiring diagram/schematic. Reconnect wires
as necessary.
RESULTS:
Reconnect, repair or replace stator AC output leads as
necessary.
Test 12- Test DPE Circuit Breaker
DISCUSSION:
The excitation (DPE) circuit breaker is connected in
series with lead 2 (or 2A) between the stator excitation (DPE)
windings and the voltage regulator. If the breaker should
open, excitation winding AC output to the Regulator will be
lost and AC ou^ut from the generator will drop to a voltage
that is commensurate with the Rotor’s residual magnetism
(about 2 to 7 volts AC). Application of fixed excitation current
p est 6) will result in an AC output voltage equal to approxi
mately one-half rated voltage.
Page 1.6-3
Test 12< Test DPE Circuit Breaker (Con
tinued)
PROCEDURE:
1. With the generator shut down, disconnect the leads from
the two breaker terminals, to prevent interaction. Then,
connect the test leads of a volt-ohm-milliammeter (VOM)
across the two circuit breaker terminals. The meter should
read continuity or a very small resistance.
a. If meter indicates 'continuity' or a small resistance, go
to Step 2.
b. If the meter reads 'infinity' replace the circuit breaker.
2. Reconnect the two leads to the circuit breaker terminals.
3. Start the generator engine.
4. Check the generator's AC output voltage (see Test 1).
a. if AC output voltage is excessively low, go to Step 5.
b. If AC output voltage is normal, discontinue tests.
5. Connect a jumper wire across the two terminals of the
excitation (DPE) circuit breaker. Again, check the unit’s AC
output voltage.
RESULTS:
1. In Step 1, if the meter reads 'infinity' it should be replaced.
2. If AC output voltage was excessively low in Step 4, but
normal in Step 5, replace the excitation (DPE) circuit breaker.
RESULTS:
1. If the VOM indicated excitation winding resistance in Step
4, but read 'infinity' in Step 6, the thermal protector will have
to be bypassed as follows:
a. Cut Wire 2 as close as possible to the end of Wire 5.
b. Strip the Insulation from the end of Wire 2 that goes to
the excitation circuit breaker.
c. Strip the iunsulation from the end of Wire 5.
d. Connect the stripped ends of Wire 2 and 5, retain with
the wire nut.
2. If the meter indicated excitation winding resistance In both
Steps 4 and 5, go to Test 14.
Figure 32. Thermal Protector In the Circuit
Test 13- Test Thermal Protector
DISCUSSION:
Also see 'THERMAL PROTECTOR' on Page 1.1-4. A
thermal protector that has failed open will cause the same
effects as an excitation circuit breaker that has failed open.
PROCEDURE:
1. Disconnect lead 2 from the excitation circuit breaker.
2. Disconnect lead 6 from the Voltage Regulator.
3. Locate lead 5. This lead is brought out of the Stator and is
unattached. A wire nut covers its end.
4. Connect the test leads of a VOM across leads 5 and 6. The
meter should read a small resistance (the resistance of the
Stator excitation winding).
5. Now, connect the VOM test leads across leads 2 and 6.
Again, the resistance of the Stator excitation windings shouid
be indicated (about 0.73 ohm for 10 kW units; 1.00 ohm for 8
kW units).
A. Pictorial
Figure 33. Thermal Protector Bypassed
B. Schematic
CXCrTATtON
rr*T)ON I
^ ^ WINDINO
-.-t
ÓO
TO EXCrTATION
2A
A. Pictorial
Test 14- Test Stator DPE Windings
DISCUSSION:
An open condition in the stator excitation windings wiii
result in loss of excitation output to the Voltage Regulator.
The Regulator will then shut down and generator AC output
voltage will drop to a value commensurate with Rotor residuai
magnetism (about 2-7 volts).
A grounded or shorted condition will also result in prob
lems with generator AC output. This test will test the Stator
excitation windings for (a) open condition, and (b) for a
grounded condition.
ClftClHT BBBAKER
B. Schematic
Page 1.6-4
NOTE: Before attempting to test the Stator excitation
winding, be sure the thermal protector has not failed
open. See Teat 13.
PR^OCEDURE:
1. Disconnect Wire 2 from the excitation circuit breaker (CB4).
2. Disconnect Wire 6 from the Voltage Regulator.
3. Use a VOM to test the resistance of the excitation windings.
Connect the VOM test leads across leads 2 and 6. The VOM
should indicate the resistance of the excitation windings.
a. For 8 kW units, reading should be approximately 1.00
ohm (plus or minus 10%).
b. For 10 kW units, resistance should be approximately
0.73 ohm (plus or minus 10%).
4. Now, set the VOM to a high resistance scale such as
"Rxl 0,000’ or *Rx1 K’. Zero the meter. Connect one VOM test
lead to Wire 6, the other test iead to a clean frame ground on
the Stator. The meter should read 'Infinity'.
RESULTS:
1. If stator excitation windings fall the test, replace the Stator
assembly.
2. If excitation windings check good, go to Test 15.
Test 15- Test Stator AC Power Windings
DISCUSSION:
An open or shorted condition in the Stator will adversely
affect generator AC voltage output. This test will check the
AC power windings for (a) open condition, (b) grounded
condition, and (c) short between parallel windings.
PR^OCEDURE:
1. Disconnect and isolate Stator leads 11,22,33 and 44. Also
disconnect and isolate Stator leads 5 and 6.
2. Set a VOM to Its 'Rxl' scale and zero the meter.
3. Connect the VOM test leads across stator leads 11 and
22.
a. For 8 kW units, the meter should read approximately
0.21 ohm.
b. For 10 kW units, the VOM should indicate approximately
0.14 ohm.
NOTE: The actual realatance will vary slightly with tem
perature, with a nominal variation as much as plus or
mlnua 10 percent.
4. Connect the VOM test leads across stator leads 33 and 44.
Resistance readings should be the same as In Step 3(a) and
3(b).
5. Now, set the VOM to a high resistance scale, such as
’Rx10,000' or 'RxlK'. Zero the meter. Connect one meter
test lead to stator lead 11, the other test lead to stator lead
33.
a. The meter should read 'infinity'.
b. Any reading other than 'infinity' Indicates a short be
tween parallel windings.
6. With VOM still set for a high resistance, connect one VOM
test lead to stator lead 11, the other test lead to a clean frame
ground on the stator. Repeat the test with one test lead
attached to stator lead 33 and the other connected to a clean
frame ground on the stator.
a. The VOM should read '1011011/.
b. Any reading other than 'Infinity' Indicates a grounded
condition.
7. With the VOM still set for a high resistance, connect one
VOM test lead to stator lead 11, the other to stator lead 5.
Repeat the test with one VOM test lead connected to stator
lead 33, the other to stator lead 5.
a. In both cases, the meter should read 'Infinity'.
b. Any reading other than 'infinity' Indicates a short be
tween windings.
RESULTS:
1. If any reading is bad, replace the stator assembly.
2. If stator checks good, go to Test 16.
Test 16- Check Sensing Leads
DISCUSSION:
The Voltage Regulator must sense ACTUAL AC power
winding voltage. Itr must then electronically 'compare' the
ACTUAL voltage to a REFERENCE voltage that is preset In
the Regulator. The Regulator acts to maintain an actual
voltage that is the same as the reference voltage by regulat
ing excitation current flow to the Rotor.
If ACTUAL voltage sensing signals to the Regulator
become lost for any reason, the normal reaction of most
Regulators would be to think' that ACTUAL voltage Is too
low. The Regulator would then Increase excitation current
flow to the Rotor in an attempt to increase the ACTUAL
voltage. That is, the Regulator and Rotor would go to a 'Full
Field''^ condition and the generator’s AC output vdtage would
go to a very high maximum value.
However, the Voltage Regulator used on RV/IM models
is equipped with a 'sensing loss cutout' feature. That is, when
loss of sensing signals occurs, the Voltage Regulator will shut
down. When the Regulator shuts down, a complete loss of
excitation current flow to the Rotor will occur. The actual AC
output voltage will then drop dramatically to a value commen
surate with Rotor residual magnetism (about 2 to 7 volts AC).
PROCEDURE:
1. With the generator running, observe the red LED (light
emitting diode) on the AC voltage regulator. If sensing voltage
is available to the regulator, the light should be ON.
a. if the light is OUT, complete Step 2 below.
b. If the light is ON, go to Test 17.
2. Connect an accurate AC voltmeter across the Voltage
Regulator sensing terminals (leads 11 and 22). The meter
should Indicate line-to-neutrai voltage. If not, complete the
following:
a. Carefully Inspect sensina leads 11 and 22, between the
engine control circuit board and the Voltage Regulator.
b. Inspect leads 11 and 22 between the engine control
circuit board and the AC connection panel.
c. Use a VOM to check sensing leads 11 and 22 for an
open or shorted condition.
RESULTS:
1. Reconnect, repair or replace any damaged, open, shorted
or defective sensing leads.
2. If sensing leads are good, go to Test 17.
Test 17- Check Voltage Regulator
DISCUSSION:
The Voltage Regulator Is discussed under Test 16 above, as
well as on Page 1.1-4. The Regulator Is equipped with two
safety features, as follows:
Page 1.6<^
Test 17- Check Voltage Regulator (Con
tinued)
1. Sensing loss shutdown- if sensing is not availabie to the
Regulator (sensing leads 11 and 22), the Regulator will shut
down.
a. With the Regulator shut down, loss of regulated excita
tion current to the Rotor will occur.
b. The generator’s AC output voltage will drop to a value
commensurate with Rotor residual magnetism (approxi
mately 2-7 volts AC).
c. The red LED (light emitting diode) on the Regulator is a
sensing indicator. The light will go OUT when sensing
signals to the Regulator (wires 11 and 22) are not avail
able. It should remain ON during operation, indicating that
sensing voltage is available.
2. Voltage limiting- maximum AC output voltage is limited to
a maximum of approximately 140-145 volts AC (llne-to-neutral).
PROCEDURE:
If a zero or low AC output voltage condition exists and
you have completed all previous tests Indicated in the Trou
bleshooting Flow Chart", you might try adjusting the Voltage
Regulator. If attempts to adjust the Regulator do not produce
positive results, replace the Regulator. Then, adjust the
Regulator and test generator operation.
Page 1.6-6
Part 2
ENGINE
MECHANICAL
NP and IM Series
RECREATIONAL
VEHICLE &
INDUSTRIAL
MOBILE
AC GENERATORS
Liquid Cooled 1.2 Liter
Gas Engine Models
SECTION
2.1
2.2
2.3
2.4
2.5
2.6
TABLE OF CONTENTS
TITLE
Basic Engine Mechanical
Timing Belt
Cylinder Head
Oil Pan and Oil Pump
Oil Seal Replacement
Engine Overhaul
Section 2.1- BASIC ENGINE MECHANICAL
This section covers some of the basic engine servicing
Introduction
tasks. Included In the Section are commonly used tightening
procedures for cylinder head bolts, manifold nuts and carbu
retor bolts. Also covered are valve clearance adjustment and
drive belt checking procedures.
Tightening Cylinder Head Boits
RetIghten cylinder head bolts while the engine Is cold, at
approximately 68* F. (20* C.). Tighten the bolts as follows:
1. Remove all spark plugs, oil pump drive gears, retainer and
bolts (Figure 1).
1. Set No. 1 cylinder at top dead center (TDC) of Its compres
sion stroke. Then, adjust valve clearance 1,2,3 and 6.
2. Set No. 4 cylinder at top dead center (TDC) of its compres
sion stroke and adjust valve clearance 4, 5, 7 and 8.
3. Set valve clearance as follows:
VALVE CLEARANCE HOT
INTAKE s 0.010 Inch (0.25mm)
EXHAUST = 0.012 Inch (0.30mm)
Figure 3. Valve Clearance Adjustments
© (2) (?) (6)
(i) d) (z)
4. When valve clearances are properly set, tighten the adjust
ing screw locknut to 8-11 foot-pounds (11-15 N-m).
2. Tighten bolts to 47-51 foot-pounds (64-69 N-m) in the
sequence shown below.
Tighten Manifoid, Exhaust Manifoid and
Carburetor Fasteners
INTAKE MANIFOLD NUTS:
Tighten to 12-15 foot-pounds (16-21 N-m).
EXHAUST MANIFOLD NUTS:
Tighten to 12-15 foot-pounds (16-21 N-m).
CARBURETOR BOLTS:
Tighten to 4.3-5.8 foot-pounds (6-8 N-m).
Adjusting Vaive Clearance
Adjust valves while engine is warm, but not running, as
foltows:
Inspect drive belts for cracks, fraying, wear, ollllness.
Checking Drive Beits
Replace, if necessary. The belts should not touch the bottom
of the pulley groove. To check belt tension, apply a force of
approximately 22 pounds (10 kg) midway between pulleys.
Belt deflection should be as follows:
NEW BELT a 0.59^).75 inch (15-19m)
USED BELTaO.71-0.87 inch (18-22mm)
Measuring Compression Pressure
Warm up the engine. Then, shut down and remove ail spark
plugs. Use a standard automotive type compression gauge.
Hold the throttle and choke valves on carburetor wide open.
Page 2.1-1
Measuring Compression Pressure (Continued)
then crank the engine and read the compression pres
sure. The pressure reading shouid be as follows:
^TANDAR^^^9278MiT5kg7clT?)at35^^
MINIMUM n 164 psi (11.5 kg/cm^) at 350 rpm
DIFFERENCE BETWEEN CYLINDERS SHOULD NOT
EXCEED 14 PSI (1.0 kg/cm^)
If the compression reading is low in any cylinder, pour a
small amount of clean engine oil into the cylinders through
the spark plug opening. Then, retest compression and eval
uate as follows:
D If compression pressure increased after adding the oil,
check for worn or damaged piston rings or worn cylinder
walls.
n If pressure did NOT increase after adding oil, valve(s)
may be sticking or seating improperly.
D If compression in any two adjacent cylinders is low and
adding oil did not increase compression, check for a
leaking head gasket
Page 2.1-2
Section 2.2- TIMING BELT
Timing Belt Precautions
Comply with the following precautions when removing,
Installing or inspecting the timing belt:
D Make sure the timing belt, pullies and belt tensioner are
free of oil and water.
□ Prior to installing the timing belt, make sure that No. 1
cylinder is at top dead center (TDC) of its compression
stroke.
D Align the arrow on the timing belt in the direction of
engine rotation.
G Remove all spark plugs before adjusting timing belt
tension.
□ Once the timing belt has been removed, DO NOT rotate
the crankshaft and camshaft separately, or the valves
will strike the piston heads.
Q Do NOT bend or twist the timing belt too tightly.
Timing Beit Removai
1. Drain the radiator.
2. Remove the radiator, fan guard and fan. See Part 4,
“ENGINE COOLING SYSTEM".
3. Remove tension from the drive belt, then remove the drive
belt.
4. Remove the crankshaft pulley.
5. Set No. 1 cylinder at top dead center (TDC) of its compres
sion stroke. Then, remove upper and lower dust covers and
gaskets.
6. Loosen timing belt tensioner and return spring, then re
move timing belt.
Timing Beit Inspection
BELT IS BROKEN;
Caused by improper han
dling, poor belt cover sealing,
coolant leakage at water
pump.
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