Guardian 4700 Operating instructions

Manual Part No. 0E1881
DIAGNOSTIC
REPAIR
MANUAL
RECREATIONAL VEHICLE GENERATOR
Model 4700
QUIETPACT®40
P.O. Box 297 • Whitewater, WI 53190
Phone: [phone] Fax: [phone]
Printed in U.S.A Revision A - 10/13/03
GENERAC
OHVI
POWERED
GENERAC OHVI INDUSTRIAL ENGINE
QUIETPACT 40G
RV SERVICELOCATOR:
1.800.333.1322
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Page 2
SAFETY
Throughout this publication, "DANGER!" and "CAUTION!" blocks are used to alert the mechanic to special
instructions concerning a particular service or operation that might be hazardous if performed incorrectly or
carelessly. PAY CLOSE ATTENTION TO THEM.
DANGER! UNDER THIS HEADING WILL BE FOUND SPECIAL INSTRUCTIONS WHICH, IF NOT COM-
PLIED WITH, COULD RESULT IN PERSONAL INJURY OR DEATH.
CAUTION! Under this heading will be found special instructions which, if not complied with, could
result in damage to equipment and/or property.
These "Safety Alerts" alone cannot eliminate the hazards that they signal. Strict compliance with these spe-
cial Instructions plus "common sense" are major accident prevention measures.
NOTICE TO USERS OF THIS MANUAL
This SERVICE MANUAL has been written and published by Generac to aid our dealers' mechanics and com-
pany service personnel when servicing the products described herein.
It is assumed that these personnel are familiar with the servicing procedures for these products, or like or
similar products manufactured and marketed by Generac. That they have been trained in the recommended
servicing procedures for these products, including the use of common hand tools and any special Generac
tools or tools from other suppliers.
Generac could not possibly know of and advise the service trade of all conceivable procedures by which a
service might be performed and of the possible hazards and/or results of each method. We have not under-
taken any such wide evaluation. Therefore, anyone who uses a procedure or tool not recommended by
Generac must first satisfy himself that neither his nor the products safety will be endangered by the service
procedure selected.
All information, illustrations and specifications in this manual are based on the latest product information
available at the time of publication.
When working on these products, remember that the electrical system and engine ignition system are capa-
ble of violent and damaging short circuits or severe electrical shocks. If you intend to perform work where
electrical terminals could be grounded or touched, the battery cables should be disconnected at the battery.
Any time the intake or exhaust openings of the engine are exposed during service, they should be covered to
prevent accidental entry of foreign material. Entry of such materials will result in extensive damage when the
engine Is started.
During any maintenance procedure, replacement fasteners must have the same measurements and strength
as the fasteners that were removed. Metric bolts and nuts have numbers that indicate their strength.
Customary bolts use radial lines to indicate strength while most customary nuts do not have strength mark-
ings. Mismatched or incorrect fasteners can cause damage, malfunction and possible injury.
REPLACEMENT PARTS
Components on Generac recreational vehicle generators are designed and manufactured to comply with
Recreational Vehicle Industry Association (RVIA) Rules and Regulations to minimize the risk of fire or explo-
sion. The use of replacement parts that are not in compliance with such Rules and Regulations could result
in a fire or explosion hazard. When servicing this equipment, It is extremely important that all components be
properly installed and tightened. If Improperly Installed and tightened, sparks could Ignite fuel vapors from
fuel system leaks.
!
!

Table of Contents
Page 1
SAFETY ............................ INSIDE FRONT COVER
SECTION 1:
GENERATOR FUNDAMENTALS ...................... 3-6
MAGNETISM ................................................................ 3
ELECTROMAGNETIC FIELDS .................................... 3
ELECTROMAGNETIC INDUCTION .............................. 3
A SIMPLE AC GENERATOR ........................................ 4
A MORE SOPHISTICATED AC GENERATOR ............ 4
FIELD BOOST .............................................................. 6
GENERATOR AC CONNECTION SYSTEM ................ 6
SECTION 2:
MAJOR GENERATOR COMPONENTS .............. 7-9
ROTOR ASSEMBLY ...................................................... 7
STATOR ASSEMBLY .................................................... 7
BRUSH HOLDER .......................................................... 7
BATTERY CHARGE COMPONENTS .......................... 8
EXCITATION CIRCUIT COMPONENTS ...................... 8
BREATHER ASSEMBLY .............................................. 9
SECTION 3:
INSULATION RESISTANCE TESTS ............ 10-12
EFFECTS OF DIRT AND MOISTURE ........................ 10
INSULATION RESISTANCE TESTERS ...................... 10
DRYING THE GENERATOR ...................................... 10
CLEANING THE GENERATOR .................................. 10
STATOR INSULATION RESISTANCE ........................ 11
TESTING ROTOR INSULATION ................................ 12
THE MEGOHMMETER .............................................. 12
SECTION 4:
MEASURING ELECTRICITY ........................ 13-15
METERS ...................................................................... 13
THE VOM .................................................................... 13
MEASURING AC VOLTAGE ...................................... 13
MEASURING DC VOLTAGE ...................................... 13
MEASURING AC FREQUENCY ................................ 14
MEASURING CURRENT ............................................ 14
MEASURING RESISTANCE ...................................... 14
ELECTRICAL UNITS .................................................. 15
OHM’S LAW ................................................................ 15
SECTION 5:
ENGINE DC CONTROL SYSTEM ................ 16-20
INTRODUCTION ........................................................ 16
OPERATIONAL ANALYSIS ........................................ 16
ENGINE CONTROLLER CIRCUIT BOARD ................ 16
BATTERY .................................................................... 18
7.5 AMP FUSE ............................................................ 19
FUEL PRIMER SWITCH ............................................ 19
START-STOP SWITCH .............................................. 19
STARTER CONTACTOR & MOTOR .......................... 20
SECTION 6:
TROUBLESHOOTING FLOWCHARTS .................. 21-29
IF PROBLEM INVOLVES AC OUTPUT ...................... 21
PROBLEM 1 -
VOLTAGE & FREQUENCY ARE BOTH
HIGH OR LOW ............................................................ 21
PROBLEM 2 -
GENERATOR PRODUCES ZERO VOLTAGE OR
RESIDUAL VOLTAGE (5-12 VAC) .............................. 22
PROBLEM 3 -
NO BATTERY CHARGE OUTPUT .............................. 23
PROBLEM 4 -
EXCESSIVE VOLTAGE/FREQUENCY DROOP
WHEN LOAD IS APPLIED .......................................... 24
PROBLEM 5 -
PRIMING FUNCTION DOES NOT WORK .................. 24
PROBLEM 6 -
ENGINE WILL NOT CRANK ...................................... 25
PROBLEM 7 -
ENGINE CRANKS BUT WILL NOT START ................ 26
PROBLEM 8 -
ENGINE STARTS HARD AND RUNS ROUGH .......... 27
PROBLEM 9 -
ENGINE STARTS THEN SHUTS DOWN .................. 28
PROBLEM 10 -
7.5 AMP (F1) FUSE BLOWING .................................. 29
SECTION 7:
DIAGNOSTIC TESTS...................................... 30-52
TEST 1 -
Check No-Load Voltage And Frequency ...................... 30
TEST 2 -
Check Engine Governor .............................................. 30
TEST 3 -
Test Excitation Circuit Breaker .................................... 31
TEST 4 -
Fixed Excitation Test/Rotor Amp Draw ..........................31
TEST 5 -
Wire Continuity ..............................................................32
TEST 6 -
Check Field Boost ........................................................ 32
TEST 7 -
Test Stator DPE Winding.............................................. 33
TEST 8 -
Check Sensing Leads/Power Windings........................ 34
TEST 9 -
Check Brush Leads ...................................................... 35
TEST 10 -
Check Brushes & Slip Rings ........................................ 35
TEST 11 -
Check Rotor Assembly ................................................ 35
TEST 12 -
Check Main Circuit Breakers ........................................ 36
TEST 13 -
Check Load Voltage & Frequency ................................ 36

TEST 14 -
Check Load Watts & Amperage .................................. 36
TEST 15 -
Check Battery Charge Output ...................................... 37
TEST 16 -
Check Battery Charge Rectifier .................................... 37
TEST 17 -
Check Battery Charge Windings/
Battery Charge Resistor .............................................. 37
TEST 18 -
Try Cranking the Engine .............................................. 38
TEST 19 -
Test Primer Switch........................................................ 38
TEST 20 -
Check Fuel Pump ........................................................ 39
TEST 21 -
Check 7.5 Amp Fuse .................................................... 40
TEST 22 -
Check Battery & Cables................................................ 40
TEST 23 -
Check Power Supply to Circuit Board .......................... 40
TEST 24 -
Check Start-Stop Switch .............................................. 41
TEST 25 -
Check Power Supply to Wire 56 .................................. 42
TEST 26 -
Check Starter Contactor .............................................. 42
TEST 27 -
Check Starter Motor...................................................... 43
TEST 28 -
Check Fuel Supply........................................................ 43
TEST 29 -
Check Wire 14 Power Supply ...................................... 44
TEST 30 -
Check Wire 18 .............................................................. 44
TEST 31 -
Check Fuel Solenoid .................................................... 44
TEST 32 -
Check Ignition Spark .................................................... 45
TEST 33 -
Check Spark Plug ........................................................ 46
TEST 34 -
Check Ignition Coil........................................................ 46
TEST 35 -
Check Valve Adjustment .............................................. 47
TEST 36 -
Check Carburetion........................................................ 48
TEST 37 -
Check Choke Solenoid ................................................ 48
TEST 38 -
Check Engine / Cylinder Leak Down Test /
Compression Test ........................................................ 50
TEST 39 -
Check Oil Pressure Switch .......................................... 50
TEST 40 -
Check Oil Temperature Switch .................................... 51
TEST 41 -
Test Choke Heater........................................................ 52
SECTION 8:
ASSEMBLY .................................................... 53-64
MAJOR DISASSEMBLY .............................................. 53
Enclosure/Panels ......................................................53
Rotor/Stator Removal .............................................. 53
Flywheel/Ignition Coil Removal ................................ 53
SECTION 9:
EXPLODED VIEWS / PART NUMBERS ........ 54-63
ENCLOSURE DRAWING .................................................. 54
GENERATOR DRAWING ............................................ 56
CONTROL PANEL DRAWING .................................... 58
GN-220 H/SH ENGINE DRAWING ............................ 60
SECTION 10:
SPECIFICATIONS & CHARTS ...................... 64-66
MAJOR FEATURES AND DIMENSIONS .................... 64
GENERATOR SPECIFICATIONS .............................. 65
NOMINAL RESISTANCES OF
GENERATOR WINDINGS AT 68°F ............................ 65
ENGINE SPEEDS AND
VOLTAGE SPECIFICATIONS .................................... 65
TORQUE SPECIFICATIONS ...................................... 66
SECTION 11:
ELECTRICAL DATA ...................................... 68-69
ELECTRICAL SCHEMATIC AND
WIRING DIAGRAM ...................................................... 68
Page 2
Table of Contents

Section 1
GENERATOR FUNDAMENTALS
MAGNETISM
Magnetism can be used to produce electricity and
electricity can be used to produce magnetism.
Much about magnetism cannot be explained by our
present knowledge. However, there are certain pat-
terns of behavior that are known. Application of these
behavior patterns has led to the development of gen-
erators, motors and numerous other devices that uti-
lize magnetism to produce and use electrical energy.
See Figure 1-1. The space surrounding a magnet is
permeated by magnetic lines of force called "flux".
These lines of force are concentrated at the magnet's
north and south poles. They are directed away from
the magnet at its north pole, travel in a loop and re-
enter the magnet at its south pole. The lines of force
form definite patterns which vary in intensity depend-
ing on the strength of the magnet. The lines of force
never cross one another. The area surrounding a
magnet in which its lines of force are effective is
called a "magnetic field".
Like poles of a magnet repel each other, while unlike
poles attract each other.
Figure 1-1. – Magnetic Lines of Force
ELECTROMAGNETIC FIELDS
All conductors through which an electric current Is
flowing have a magnetic field surrounding them. This
field is always at right angles to the conductor. If a
compass is placed near the conductor, the compass
needle will move to a right angle with the conductor.
The following rules apply:
• The greater the current flow through the conductor,
the stronger the magnetic field around the conductor.
• The increase in the number of lines of force is
directly proportional to the increase in current flow
and the field is distributed along the full length of
the conductor.
• The direction of the lines of force around a conduc-
tor can be determined by what is called the "right
hand rule". To apply this rule, place your right hand
around the conductor with the thumb pointing in the
direction of current flow. The fingers will then be
pointing in the direction of the lines of force.
NOTE: The "right hand rule" is based on the "cur-
rent flow" theory which assumes that current
flows from positive to negative. This is opposite
the "electron" theory, which states that current
flows from negative to positive.
Figure 1-2. – The Right Hand Rule
ELECTROMAGNETIC INDUCTION
An electromotive force (EMF) or voltage can be pro-
duced in a conductor by moving the conductor so that
it cuts across the lines of force of a magnetic field.
Similarly, if the magnetic lines of force are moved so
that they cut across a conductor, an EMF (voltage)
will be produced in the conductor. This is the basic
principal of the revolving field generator.
Figure 1-3, below, illustrates a simple revolving field
generator. The permanent magnet (Rotor) is rotated
so that its lines of magnetic force cut across a coil of
wires called a Stator. A voltage is then induced into
the Stator windings. If the Stator circuit is completed
by connecting a load (such as a light bulb), current
will flow in the circuit and the bulb will light.
Figure 1-3. – A Simple Revolving Field Generator
Page 3

Section 1
GENERATOR FUNDAMENTALS
A SIMPLE AC GENERATOR
Figure 1-4 shows a very simple AC Generator. The
generator consists of a rotating magnetic field called
a ROTOR and a stationary coil of wire called a STA-
TOR. The ROTOR is a permanent magnet which con-
sists of a SOUTH magnetic pole and a NORTH mag-
netic pole.
As the MOTOR turns, its magnetic field cuts across
the stationary STATOR. A voltage is induced Into the
STATOR windings. When the magnet's NORTH pole
passes the STATOR, current flows in one direction.
Current flows in the opposite direction when the mag-
net's SOUTH pole passes the STATOR. This con-
stant reversal of current flow results in an alternating
current (AC) waveform that can be diagrammed as
shown in Figure 1-5.
The ROTOR may be a 2-pole type having a single
NORTH and a single SOUTH magnetic pole. Some
ROTORS are 4-pole type with two SOUTH and two
NORTH magnetic poles. The following apply:
1. The 2-pole ROTOR must be turned at 3600 rpm to produce an
AC frequency of 60 Hertz, or at 3000 rpm to deliver an AC fre-
quency of 50 Hertz.
2. The 4-pole ROTOR must operate at 1800 rpm to deliver a 60
Hertz AC frequency or at 1500 rpm to deliver a 50 Hertz AC
frequency.
Figure 1-4. – A Simple AC Generator
Figure 1-5. – Alternating Current Sine Wave
A MORE SOPHISTICATED AC GENERATOR
Figure 1-6 represents a more sophisticated genera-
tor. A regulated direct current is delivered into the
ROTOR windings via carbon BRUSHES AND SLIP
RINGS. This results in the creation of a regulated
magnetic field around the ROTOR. As a result, a reg-
ulated voltage is induced into the STATOR.
Regulated current delivered to the ROTOR is called
"EXCITATION" current.
Figure 1-6. – A More Sophisticated Generator
See Figure 1-7 (next page). The revolving magnetic
field (ROTOR) is driven by the engine at a constant
speed. This constant speed is maintained by a
mechanical engine governor. Units with a 2-pole rotor
require an operating speed of 3600 rpm to deliver a
60 Hertz AC output. Engine governors are set to
maintain approximately 3720 rpm when no electrical
loads are connected to the generator.
S
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BR
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12
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12
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AC
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DC
CU
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OR
24
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CURRENT VOLTAGE
ONE CYCLE
0180 360
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(-)
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Page 4

Section 1
GENERATOR FUNDAMENTALS
NOTE: AC output frequency at 3720 rpm will be
about 62 Hertz. The "No-Load" is set slightly high
to prevent excessive rpm, frequency and voltage
droop under heavy electrical loading.
Generator operation may be described briefly as fol-
lows:
1. Some "residual" magnetism is normally present in the Rotor
and is sufficient to induce approximately 7 to 12 volts AC Into
the STATOR's AC power windings.
2. During startup, an engine controller circuit board delivers bat-
tery voltage to the ROTOR, via the brushes and slip rings.
a. The battery voltage is called "Field Boost".
b. Flow of direct current through the ROTOR
increases the strength of the magnetic field
above that of "residual" magnetism alone.
3. "Residual" plus "Field Boost" magnetism induces a voltage into
the Stator excitation (DPE), battery charge and AC Power
windings.
4. Excitation winding unregulated AC output is delivered to an
electronic voltage regulator, via an excitation circuit breaker.
a. A "Reference" voltage has been preset into
the Voltage Regulator.
b. An "Actual" ("sensing") voltage is delivered
to the Voltage Regulator via sensing leads
from the Stator AC power windings.
c. The Regulator "compares" the actual (sens-
ing) voltage to its pre-set reference voltage.
(1) If the actual (sensing) voltage is greater
than the pre-set reference voltage, the
Regulator will decrease the regulated cur-
rent flow to the Rotor.
(2) If the actual (sensing) voltage is less
than the pre-set reference voltage, the
Regulator will increase the regulated cur-
rent flow to the Rotor.
(3) In the manner described, the Regulator
maintains an actual (sensing) voltage that is
equal to the pre-set reference voltage.
NOTE: The Voltage Regulator also changes the
Stator excitation windings alternating current
(AC) output to direct current (DC).
5. When an electrical load is connected across the Stator power
windings, the circuit is completed and an electrical current will
flow.
6. The Rotor's magnetic field also induces a voltage Into the
Stator battery charge windings.
a. Battery charge winding AC output is deliv-
ered to a battery charge rectifier (BCR)
which changes the AC to direct current
(DC).
b. The rectified DC is then delivered to the unit
battery, to maintain the battery in a charged
state.
c. A 1 ohm, 25 watt Resistor is installed in
series with the grounded side of the battery
charge circuit.
Page 5
Figure 1-7. – Generator Operating Diagram

Section 1
GENERATOR FUNDAMENTALS
FIELD BOOST
When the engine is cranked during startup, the
engine's starter contactor is energized closed. Battery
current is then delivered to the starter motor and the
engine cranks.
Closure of the starter contactor contacts also delivers
battery voltage to Pin 13 of an Engine Controller cir-
cuit board. The battery current flows through a 47
ohm, 2 watt resistor and a field boost diode, then to
the Rotor via brushes and slip rings. This is called
"Field Boost" current.
Field boost current is delivered to the Rotor only while
the engine is cranking. The effect is to "flash the field"
every time the engine is cranked. Field boost current
helps ensure that sufficient "pickup" voltage is avail-
able on every startup to turn the Voltage Regulator on
and build AC output voltage.
NOTE: Loss of the Field Boost function may or
may not result in loss of AC power winding out-
put. If Rotor residual magnetism alone is suffi-
cient to turn the Regulator on loss of Field Boost
may go unnoticed. However, If residual magnet-
ism alone Is not enough to turn the Regulator on,
loss of the Field Boost function will result In loss
of AC power winding output to the load. The AC
output voltage will then drop to a value commen-
surate with the Rotor's residual magnetism (about
7-12 VAC).
GENERATOR AC CONNECTION SYSTEM
120 VAC OUTPUT:
The Stator AC power winding consists of two wind-
ings connected in parallel, with each winding capable
of supplying 120 volts AC.
Figure 1-8. – Power Winding Output
12
0
V
30A
P
O
WER WINDIN
G
WHITE
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G
REE
N
22P
44
BLA
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B
1
11P
33
Page 6

Section 2
MAJOR GENERATOR COMPONENTS
ROTOR ASSEMBLY
The Rotor is sometimes called the "revolving field",
since it provides the magnetic field that induces a
voltage into the stationary Stator windings. Slip rings
on the Rotor shaft allow excitation current from the
voltage regulator to be delivered to the Rotor wind-
ings. The Rotor is directly coupled to the engine
crankshaft.
All generator models in this manual utilize a 2-pole
Rotor, i.e., one having a single north and a single
south pole. This type of Rotor must be driven at 3600
rpm for a 60 Hertz AC output, or at 3000 rpm for a 50
Hertz output.
Slip rings may be cleaned. If dull or tarnished, clean
them with fine sandpaper (a 400 grit wet sandpaper is
recommended). DO NOT USE ANY METALLIC GRIT
OR ABRASIVE TO CLEAN SLIP RINGS.
STATOR ASSEMBLY
The Stator is "sandwiched" between the engine
adapter and rear bearing carrier and retained in that
position by four Stator studs. Windings Included in the
Stator assembly are (a) dual AC power windings, (b)
an excitation or DPE winding, and (c) a battery
charge winding. A total of eleven (11) leads are
brought out of the Stator as follows:
1. Four (4) Stator power winding output leads (Wires No. 11P,
22P, 33 and 44). These leads deliver power to connected elec-
trical loads.
2. Stator Power winding "sensing" leads (11S and 22S). These
leads deliver an "actual voltage signal to the electronic Voltage
Regulator.
3. Two excitation winding output leads (No. 2 and 6). These leads
deliver unregulated excitation current to the voltage regulator.
4. Three (3) battery charge output leads (No. 55, 66 and 77).
Figure 2-2. – Stator Output Leads
BRUSH HOLDER
The brush holder is retained in the rear bearing carri-
er by two M5 screws. It retains two brushes, which
contact the Rotor slip rings and allow current flow
from stationary parts to the revolving Rotor. The posi-
tive (+) brush is located nearest the Rotor bearing.
2
6
11P
11S
22P
22S
33
44
66
55
77
Leads 2 & 6 =Stator Excitation Winding
Leads 11S & 22S = Voltage Sensing Leads
Leads 11P & 22P, 33 & 44 = AC Power Windings
Leads 55, 66, 77 = Battery Charge Windings
Page 7
Figure 2-1. Exploded View of Generator
3
1
2
4
5
6
1. BRUSH HOLDER
2. REAR BEARING CARRIER
3. BEARING
4. ROTOR
5. STATOR
6. ENGINE ADAPTOR

Section 2
MAJOR GENERATOR COMPONENTS
Figure 2-3. – Brush Holder
BATTERY CHARGE COMPONENTS
The Stator incorporates dual battery charge windings.
A battery charge rectifier (BCR) changes the AC out-
put of these windings to direct current (DC). Battery
charge winding output is delivered to the unit battery
via the rectifier, a 7.5 amp fuse and Wire No. 13. A 1
ohm, 25 watt resistor is connected in series with the
grounded side of the circuit.
Figure 2-4. – Battery Charge Circuit
EXCITATION CIRCUIT COMPONENTS
GENERAL:
During operation, the Rotor's magnetic field induces a
voltage and current flow into the Stator excitation
winding. The resultant AC output is delivered to a
voltage regulator via an excitation circuit breaker
(CB3).
Figure 2-5. – Schematic- Excitation Circuit
EXCITATION CIRCUIT BREAKER:
The excitation circuit breaker (CB3) is self-resetting
and cannot be reset manually. Should the breaker
open for any reason, excitation current flow to the
Rotor will be lost. The unit's AC output voltage will
then drop to a value commensurate with the Rotor's
residual magnetism (about 7-12 VAC).
Figure 2-6. – Excitation Circuit Breaker
VOLTAGE REGULATOR:
Six (6) leads are connected to the voltage regulator
as follows:
• Two (2) SENSING leads deliver ACTUAL AC out-
put voltage signals to the regulator. These are
Wires No. 11S and 22S.
• Two (2) leads (No. 2A and 6) deliver Stator excita-
tion winding AC output to the regulator.
• Two (2) leads (0K and 4) deliver the regulated
direct current to the Rotor, via brushes and slip
rings.
2A
2
DPE WINDIN
G
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OR
P
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G
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FIELD
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B
3
0K
2
2A
22
S
4
6
4
11
S
BATTERY
C
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E WINDIN
G
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BATTER
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55
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5
77
B
CR
66
66
BCR = Battery Char
g
e Rectifie
r
R1 = 1 Ohm, 25 Watt Resistor
BRUSHES
Page 8

Section 2
MAJOR GENERATOR COMPONENTS
Figure 2-7. – Voltage Regulator
The regulator mounts a "VOLTAGE ADJUST" poten-
tiometer, used for adjustment of the pre-set REFER-
ENCE voltage. A lamp (LED) will turn on to indicate
that SENSING voltage is available to the regulator
and the regulator is turned on.
The regulator mounts a “VOLTAGE ADJUST” poten-
tiometer, used for adjustment of the pre-set REFER-
ENCE voltage. A lamp (LED) will turn on to indicate
that SENSING voltage is available to the regulator
and that the regulator is turned on.
ADJUSTMENT PROCEDURE:
With the frequency set at 62.5 Hertz and no load on
the generator, slowly turn the voltage adjust pot on
the voltage regulator until 124 VAC is measured. If
voltage is not adjustable, proceed to Section 6 -
Troubleshooting; Problem 2.
NOTE: If, for any reason, sensing voltage to the
regulator is lost, the regulator will shut down and
excitation output to the Rotor will be lost. The AC
output voltage will then drop to a value that is
commensurate with Rotor residual magnetism
(about 7-12 VAC). Without this automatic shut-
down feature, loss of sensing (actual) voltage to
the regulator would result in a “full field” or “full
excitation” condition and an extremely high AC
output voltage.
NOTE: Adjustment of the regulator's "VOLTAGE
ADJUST" potentiometer must be done only when
the unit is running at its correct governed no-load
speed. Speed is correct when the unit's no-load
AC output frequency is about 62.5 Hertz. At the
stated frequency, AC output voltage should be
about 124 volts.
BREATHER ASSEMBLY
DESCRIPTION:
A crankcase breather is located in the rocker arm
cover of horizontal crankshaft engines (Figure 2-8).
The breather serves to maintain a reduced pressure
in the engine crankcase, to prevent oil from being
forced past the oil seals, gaskets or piston rings.
The CHECK VALVE allows excess pressure to be
vented out of the crankcase and to atmosphere
through the BREATHER TUBE. Two small DRAIN
HOLES allow condensed oil vapors to return to the
crankcase.
Figure 2-8. – Crankcase Breather
INSPECTION:
1. Remove the breather tube. Check tube for cracks, hardening or
other damage. Replace if necessary.
2. Clean the rocker arm cover in commercial solvent.
3. Make sure the two small drain holes are open. If necessary,
use a length of wire to open the holes.
4. Check the rivets that retain the check valve, make sure they
are tight.
5. The breather plate is retained in the rocker arm cover with a
continuous bead of Type 103 black RTV sealant. This sealant
must not leak. Test the sealant for leakage as follows:
a. Seal all holes on the breather plate.
b. Apply air pressure of 5 psi (0.352 kg/cm ) through the
breather hose hole. No leakage must be observed.
c. If necessary, reseal the plate with Type 103 black RTV
sealant.
BREATHER
TUBE
CHECK
VALVE
DRAIN
HOLE
ROCKER
ARM
COVER
VOLTAGE
ADJUST POT
LED
11S 22S
4OK
6
2A
Page 9

Section 3
INSULATION RESISTANCE TESTS
EFFECTS OF DIRT AND MOISTURE
Moisture and dirt are detrimental to the continued
good operation of any generator set.
If moisture is allowed to remain in contact with the
Stator and Rotor windings, some of the moisture will
be retained in voids and cracks of the winding
Insulation. This will result in a reduced Insulation
resistance and, eventually, the unit's AC output will be
affected.
Insulation used in the generator is moisture resistant.
However, prolonged exposure to moisture will gradu-
ally reduce the resistance of the winding insulation.
Dirt can make the problem worse, since it tends to
hold moisture Into contact with the windings. Salt, as
from sea air, contributes to the problem since salt can
absorb moisture from the air. When salt and moisture
combine, they make a good electrical conductor.
Because of the detrimental affects of dirt and mois-
ture, the generator should be kept as clean and as
dry as possible. Rotor and Stator 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 accumulated moisture.
After drying, perform a second insulation resistance
test. If resistance is still low after drying, replacement
of the defective Rotor or Stator may be required.
INSULATION RESISTANCE TESTERS
Figure 3-1 shows one kind of hi-pot tester. The tester
shown has a "Breakdown" lamp that will glow during
the test procedure to indicate an insulation break-
down in the winding being tested.
Figure 3-1. – One Type of Hi-Pot Tester
DANGER!: INSULATION RESISTANCE
TESTERS SUCH AS HI-POT TESTERS AND
MEGOHMMETERS ARE A SOURCE OF HIGH
AND DANGEROUS ELECTRICAL VOLTAGE.
FOLLOW THE TESTER MANUFACTURER'S
INSTRUCTIONS CAREFULLY. USE COMMON
SENSE TO AVOID DANGEROUS ELECTRICAL
SHOCK
DRYING THE GENERATOR
GENERAL:
If tests indicate the insulation resistance of a winding
is below a safe value, the winding should be dried
before operating the generator. Some recommended
drying procedures Include (a) heating units and (b)
forced air.
HEATING UNITS:
If drying is needed, the generator can be enclosed in
a covering. Heating units can then be installed to
raise the temperature about 15°-18° F. (8°-10° C.)
above ambient temperature.
FORCED AIR:
Portable forced air heaters can be used to dry the
generator. Direct the heated air into the generator’s
air intake openings. Remove the voltage regulator
and run the unit at no-load. Air temperature at the
point of entry into the generator should not exceed
150° F. (66° C.).
CLEANING THE GENERATOR
GENERAL:
The generator can be cleaned properly only while it is
disassembled. The cleaning method used should be
determined by the type of dirt to be removed. Be sure
to dry the unit after it has been cleaned.
NOTE: A shop that repairs electric motors may be
able to assist you with the proper cleaning of gen-
erator windings. Such shops are often experi-
enced In special problems such as a sea coast
environment, marine or wetland applications,
mining, etc.
USING SOLVENTS FOR CLEANING:
If dirt contains oil or grease a solvent is generally
required. Only petroleum distillates should be used to
clean electrical components. Recommended are
safety type petroleum solvents having a flash point
greater than 100° F. (38° C.).
!
Page 10

Section 3
INSULATION RESISTANCE TESTS
CAUTION!: SOME GENERATORS MAY USE
EPOXY OR POLYESTER BASE WINDING
VARNISHES. USE SOLVENTS THAT WILL
NOT ATTACK SUCH MATERIALS.
Use a soft brush or cloth to apply the solvent. Be care-
ful to avoid damage to wire or winding insulation. After
cleaning, dry all components thoroughly using mois-
ture-free, low-pressure compressed air.
DANGER!: DO NOT ATTEMPT TO WORK
WITH SOLVENTS IN ANY ENCLOSED AREA.
PROVIDE ADEQUATE VENTILATION WHEN
WORKING WITH SOLVENTS. WITHOUT ADE-
QUATE VENTILATION, FIRE, EXPLOSION OR
HEALTH HAZARDS MAY EXIST . WEAR EYE
PROTECTION. WEAR RUBBER GLOVES TO
PROTECT THE HANDS.
CLOTH OR COMPRESSED AIR:
For small parts or when dry dirt is to be removed, a
dry cloth may be satisfactory. Wipe the parts clean,
then use low pressure air at 30 psi (206 Kpa) to blow
dust away.
BRUSHING AND VACUUM CLEANING:
Brushing with a soft bristle brush followed by vacuum
cleaning is a good method of removing dust and dirt.
Use the soft brush to loosen the dirt, then remove it
with the vacuum.
STATOR INSULATION RESISTANCE
GENERAL:
Insulation resistance is a measure of the Integrity of
the insulating materials that separate electrical wind-
ings from the generator's steel core. This resistance
can degrade over time due to the presence of conta-
minants, dust, dirt, grease and especially moisture).
The normal Insulation resistance for generator wind-
ings is on the order of "millions of ohms" or
"megohms".
When checking the insulation resistance, follow the
tester manufacturer's Instructions carefully. Do NOT
exceed the applied voltages recommended in this
manual. Do NOT apply the voltage longer than one
(1) second.
CAUTION!: DO NOT connect the Hi-Pot Tester
or Megohmmeter test leads to any leads that
are routed into the generator control panel.
Connect the tester leads to the Stator or
Rotor leads only.
STATOR SHORT-TO-GROUND TESTS:
See Figure 3-2. To test the Stator for a short-to-
ground condition, proceed as follows:
1. Disconnect and Isolate all Stator leads as follows:
a. Disconnect sensing leads 11S and 22S
from the voltage regulator.
b. Disconnect excitation winding lead No. 6
from the voltage regulator.
c. Disconnect excitation lead No. 2 from the
excitation circuit breaker (CB3).
d. Disconnect battery charge winding leads
No. 66 and 77 from the battery charge recti-
fier (BCR).
e. Disconnect battery charge winding lead No.
55 from the battery charge resistor (R1).
f. At the main circuit breakers, disconnect AC
power leads No. 11P and 33.
g. At the 4-tab ground terminal (GT), discon-
nect Stator power leads No. 22P and 44.
2. When all leads have been disconnected as outlined in Step 1
above, test for a short-to-ground condition as follows:
a. Connect the terminal ends of all Stator
leads together (11S, 22S, 11P, 22P, 33, 44,
2,6, 55, 66, 77).
b. Follow the tester manufacturer's instructions
carefully. Connect the tester leads across
all Stator leads and to frame ground on the
Stator can. Apply a voltage of 1500 volts.
Do NOT apply voltage longer than one (1)
second.
If the test Indicates a breakdown in Insulation, the
Stator should be cleaned, dried and re-tested. If the
winding fails the second test (after cleaning and dry-
ing), replace the Stator assembly.
TEST BETWEEN ISOLATED WINDINGS:
1. Follow the tester manufacturer's instructions carefully. Connect
the tester test leads across Stator leads No. 11P and 2. Apply
a voltage of 1500 volts- DO NOT EXCEED 1 SECOND.
2. Repeat Step 1 with the tester leads connected across the fol-
lowing Stator leads:
a. Across Wires No. 33 and 2.
b. Across Wires No. 11P and 66.
c. Across Wires No. 33 and 66.
d. Across Wires No. 2 and 66.
If a breakdown in the insulation between isolated
windings is indicated, clean and dry the Stator. Then,
repeat the test. If the Stator fails the second test,
replace the Stator assembly.
!
!
!
Page 11

Section 3
INSULATION RESISTANCE TESTS
TEST BETWEEN PARALLEL WINDINGS:
Connect the tester leads across Stator leads No. 11P
and 33. Apply a voltage of 1500 volts. If an insulation
breakdown is indicated, clean and dry the Stator.
Then, repeat the test between parallel windings. If the
Stator fails the second test, replace it.
Figure 3-2. – Stator Leads
TESTING ROTOR INSULATION
To test the Rotor for insulation breakdown, proceed
as follows:
1. Disconnect wires from the Rotor brushes or remove the brush
holders with brushes.
2. Connect the tester positive (+) test lead to the positive (+) slip
ring (nearest the Rotor bearing). Connect the tester negative (-)
test lead to a clean frame ground (like the Rotor shaft).
Figure 3-3. – Rotor Test Points
3. Apply 1000 volts. DO NOT APPLY VOLTAGE LONGER THAN
1 SECOND.
If an insulation breakdown is indicated, clean and dry
the Rotor then repeat the test. Replace the Rotor if it
fails the second test (after cleaning and drying).
THE MEGOHMMETER
GENERAL:
A megohmmeter, often called a "megger", consists of
a meter calibrated in megohms and a power supply.
Use a power supply of 1500 volts when testing
Stators; or 1000 volts when testing the Rotor. DO
NOT APPLY VOLTAGE LONGER THAN ONE (1)
SECOND.
TESTING STATOR INSULATION:
All parts that might be damaged by the high megger
voltages must be disconnected before testing. Isolate
all Stator leads (Figure 3-2) and connect all of the
Stator leads together. FOLLOW THE MEGGER
MANUFACTURER'S INSTRUCTIONS CAREFULLY.
Use a megger power setting of 1500 volts. Connect
one megger test lead to the junction of all Stator
leads, the other test lead to frame ground on the
Stator can. Read the number of megohms on the
meter.
The MINIMUM acceptable megger reading for Stators
may be calculated using the following formula:
EXAMPLE: Generator is rated at 120 volts AC.
Divide "120" by "1000" to obtain "0.12". Then add
"1" to obtain "1.12" megohms. Minimum
Insulation resistance for a 120 VAC Stator Is 1.12
megohms.
If the Stator insulation resistance is less than the cal-
culated minimum resistance, clean and dry the Stator.
Then, repeat the test. If resistance is still low, replace
the Stator.
Use the Megger to test for shorts between isolated
windings as outlined "Stator Insulation Resistance".
Also test between parallel windings. See "Test
Between Parallel Windings"on this page.
TESTING ROTOR INSULATION:
Apply a voltage of 1000 volts across the Rotor posi-
tive (+) slip ring (nearest the rotor bearing), and a
clean frame ground (i.e. the Rotor Shaft). DO NOT
EXCEED 1000 VOLTS AND DO NOT APPLY VOLT-
AGE LONGER THAN 1 SECOND. FOLLOW THE
MEGGER MANUFACTURER'S INSTRUCTIONS
CAREFULLY.
ROTOR MINIMUM INSULATION RESISTANCE:
1.5 megohms
POSITIVE (+)
TEST LEAD
2
6
11P
11S
22P
22S
33
44
66
55
77
Leads 2 & 6 =Stator Excitation Winding
Leads 11S & 22S = Voltage Sensing Leads
Leads 11P & 22P, 33 & 44 = AC Power Windings
Leads 55, 66, 77 = Battery Charge Windings
Page 12
MINIMUM INSULATION GENERATOR RATED VOLTS
RESISTANCE = __________________________ +1
(in "Megohms") 1000

Section 4
MEASURING ELECTRICITY
METERS
Devices used to measure electrical properties are
called meters. Meters are available that allow one to
measure (a) AC voltage, (b) DC voltage, (c) AC fre-
quency, and (d) resistance In ohms. The following
apply:
❏To measure AC voltage, use an AC voltmeter.
❏To measure DC voltage, use a DC voltmeter.
❏Use a frequency meter to measure AC frequency In
"Hertz" or "cycles per second"..
❏Use an ohmmeter to read circuit resistance, in
"ohms".
THE VOM
A meter that will permit both voltage and resistance to
be read is the "volt-ohm-milliammeter" or "VOM".
Some VOM's are of the "analog" type (not shown).
These meters display the value being measured by
physically deflecting a needle across a graduated
scale. The scale used must be Interpreted by the
user.
"Digital" VOM's (Figure 4-1) are also available and
are generally very accurate. Digital meters display the
measured values directly by converting the values to
numbers.
NOTE: Standard AC voltmeters react to the AVER-
AGE value of alternating current. When working
with AC, the effective value is used. For that rea-
son a different scale is used on an AC voltmeter.
The scale is marked with the effective or "rms"
value even though the meter actually reacts to the
average value. That is why the AC voltmeter will
give an Incorrect reading if used to measure
direct current (DC).
Figure 4-1. – Digital VOM
MEASURING AC VOLTAGE
An accurate AC voltmeter or a VOM may be used to
read the generator's AC output voltage. The following
apply:
1. Always read the generator's AC output voltage only at the
unit's rated operating speed and AC frequency.
2. The generator's voltage regulator can be adjusted for correct
output voltage only while the unit is operating at its correct
rated speed and frequency.
3. Only an AC voltmeter may be used to measure AC voltage. DO
NOT USE A DC VOLTMETER FOR THIS PURPOSE.
DANGER!: RV GENERATORS PRODUCE
HIGH AND DANGEROUS VOLTAGES. CON-
TACT WITH HIGH VOLTAGE TERMINALS
WILL RESULT IN DANGEROUS AND POSSI-
BLY LETHAL ELECTRICAL SHOCK.
MEASURING DC VOLTAGE
A DC voltmeter or a VOM may be used to measure
DC voltages. Always observe the following rules:
1. Always observe correct DC polarity.
a. Some VOM's may be equipped with a polar-
ity switch.
b. On meters that do not have a polarity
switch, DC polarity must be reversed by
reversing the test leads.
2. Before reading a DC voltage, always set the meter to a higher
voltage scale than the anticipated reading. if in doubt, start at
the highest scale and adjust the scale downward until correct
readings are obtained.
3. The design of some meters is based on the "current flow" theo-
ry while others are based on the "electron flow" theory.
a. The "current flow" theory assumes that
direct current flows from the positive (+) to
the negative (-).
b. The "electron flow" theory assumes that
current flows from negative (-) to positive
(+).
NOTE: When testing generators, the "current
flow" theory is applied. That is, current is
assumed to flow from positive (+) to negative (-).
!
Page 13

Section 4
MEASURING ELECTRICITY
MEASURING AC FREQUENCY
The generator's AC output frequency is proportional
to Rotor speed. Generators equipped with a 2-pole
Rotor must operate at 3600 rpm to supply a frequen-
cy of 60 Hertz. Units with 4-pole Rotor must run at
1800 rpm to deliver 60 Hertz.
Correct engine and Rotor speed is maintained by an
engine speed governor. For models rated 60 Hertz,
the governor is generally set to maintain a no-load
frequency of about 62 Hertz with a corresponding out-
put voltage of about 124 volts AC line-to-neutral.
Engine speed and frequency at no-load are set slight-
ly high to prevent excessive rpm and frequency droop
under heavy electrical loading.
MEASURING CURRENT
To read the current flow, in AMPERES, a clamp-on
ammeter may be used. This type of meter indicates
current flow through a conductor by measuring the
strength of the magnetic field around that conductor.
The meter consists essentially of a current trans-
former with a split core and a rectifier type instrument
connected to the secondary. The primary of the cur-
rent transformer is the conductor through which the
current to be measured flows. The split core allows
the Instrument to be clamped around the conductor
without disconnecting it.
Current flowing through a conductor may be mea-
sured safely and easily. A line-splitter can be used to
measure current in a cord without separating the con-
ductors.
Figure 4-2. – Clamp-On Ammeter
Figure 4-3. – A Line-Splitter
NOTE: If the physical size of the conductor or
ammeter capacity does not permit all lines to be
measured simultaneously, measure current flow
in each individual line. Then, add the Individual
readings.
MEASURING RESISTANCE
The volt-ohm-milliammeter may be used to measure
the resistance in a circuit. Resistance values can be
very valuable when testing coils or windings, such as
the Stator and Rotor windings.
When testing Stator windings, keep in mind that the
resistance of these windings is very low. Some
meters are not capable of reading such a low resis-
tance and will simply read "continuity".
If proper procedures are used, the following condi-
tions can be detected using a VOM:
❏A "short-to-ground" condition in any Stator or Rotor
winding.
❏Shorting together of any two parallel Stator wind-
ings.
❏Shorting together of any two isolated Stator wind-
ings.
❏An open condition in any Stator or Rotor winding.
Component testing may require a specific resistance
value or a test for “infinity” or “continuity.” Infinity is an
OPEN condition between two electrical points, which
would read as no resistance on a VOM. Continuity is
a closed condition between two electrical points,
which would be indicated as very low resistance or
“ZERO” on a VOM.
Page 14

Section 4
MEASURING ELECTRICITY
ELECTRICAL UNITS
AMPERE:
The rate of electron flow in a circuit is represented by
the AMPERE. The ampere is the number of electrons
flowing past a given point at a given time. One
AMPERE is equal to just slightly more than six thou-
sand million billion electrons per second.
With alternating current (AC), the electrons flow first
in one direction, then reverse and move in the oppo-
site direction. They will repeat this cycle at regular
intervals. A wave diagram, called a "sine wave"
shows that current goes from zero to maximum posi-
tive value, then reverses and goes from zero to maxi-
mum negative value. Two reversals of current flow is
called a cycle. The number of cycles per second is
called frequency and is usually stated in "Hertz".
VOLT:
The VOLT is the unit used to measure electrical
PRESSURE, or the difference in electrical potential
that causes electrons to flow. Very few electrons will
flow when voltage is weak. More electrons will flow as
voltage becomes stronger. VOLTAGE may be consid-
ered to be a state of unbalance and current flow as an
attempt to regain balance. One volt is the amount of
EMF that will cause a current of 1 ampere to flow
through 1 ohm of resistance.
Figure 4-4. – Electrical Units
OHM:
The OHM is the unit of RESISTANCE. In every circuit
there is a natural resistance or opposition to the flow
of electrons. When an EMF is applied to a complete
circuit, the electrons are forced to flow in a single
direction rather than their free or orbiting pattern. The
resistance of a conductor depends on (a) its physical
makeup, (b) its cross-sectional area, (c) its length,
and (d) its temperature. As the conductor's tempera-
ture increases, its resistance increases in direct pro-
portion. One (1) ohm of resistance will permit one (1)
ampere of current to flow when one (1) volt of electro-
motive force (EMF) is applied.
OHM'S LAW
A definite and exact relationship exists between
VOLTS, OHMS and AMPERES. The value of one can
be calculated when the value of the other two are
known. Ohm's Law states that in any circuit the current
will increase when voltage increases but resistance
remains the same, and current will decrease when
resistance Increases and voltage remains the same.
Figure 4-5.
If AMPERES is unknown while VOLTS and OHMS
are known, use the following formula:
AMPERES = VOLTS
OHMS
If VOLTS is unknown while AMPERES and OHMS
are known, use the following formula:
VOLTS = AMPERES x OHMS
If OHMS is unknown but VOLTS and AMPERES are
known, use the following:
OHMS = VOLTS
AMPERES
VOLTS
(E)
AMPS
(I)
OHMS
(R)
-+
AMPERE - Unit measuring rate of
current flow (number of electrons
past a given point)
OHM - Unit measuring resistance
or opposition to flow
VOLT - Unit measuring force or
difference in potential
causing current flow
Conductor of a
Circuit
Page 15

Section 5
ENGINE DC CONTROL SYSTEM
INTRODUCTION
The engine DC control system includes all compo-
nents necessary for the operation of the engine.
Operation includes rest, priming, cranking, starting,
running and shutdown. The system is shown
schematically In Figure 5-1.
OPERATIONAL ANALYSIS
CIRCUIT CONDITION- REST:
Battery voltage is available to the engine controller
circuit board (PCB) from the unit BATTERY and via
(a) the RED battery cable, Wire 13, a 7.5 amp FUSE
(F1), Wire 15 and circuit board Terminal J3. However,
circuit board action is holding the circuit open and no
action can occur.
Battery output is available to the contacts of a
STARTER CONTACTOR (SC), but the contacts are
open.
Battery voltage is also delivered to the FUEL
PRIMER SWITCH (SW2). The switch is open and the
circuit is incomplete.
CIRCUIT CONDITION- PRIMING:
When the FUEL PRIMER SWITCH (SW2) is closed by
the operator, battery voltage is delivered across the
closed switch contacts and to the FUEL PUMP (FP)
via Wire 14A. The FUEL SOLENOID (FS) will be ener-
gized open via Wire 14 during cranking and running.
CIRCUIT CONDITION- CRANKING:
When the START-STOP SWITCH (SW1) is held at
"START" position, Wire 17 from the engine controller
circuit board is connected to frame ground. Circuit
board action will then deliver battery voltage to (a) a
STARTER CONTACTOR (SC) via Wire 56, and to an
automatic CHOKE SOLENOID (CS) via Wire 90.
When battery voltage energizes the STARTER CON-
TACTOR (SC), its contacts close and battery output
is delivered to the STARTER MOTOR (SM) via Wire
16. The STARTER MOTOR (SM) energizes and the
engine cranks. When the STARTER CONTACTOR
(SC) closes, battery voltage is delivered to the engine
controller board for field boost.
CIRCUIT CONDITION-CRANKING:
While cranking, the CHOKE SOLENOID (CS) is ener-
gized cyclically by circuit board action (two seconds
on, two seconds off).
Also while cranking, circuit board action delivers bat-
tery voltage to the Wire 14/14A circuit. This energizes
the FUEL PUMP (FP) ,FUEL SOLENOID (FS) and
CHOKE HEATER (CH).
Circuit board action holds open Wire 18A to common
ground. The Magneto will induce a spark during cranking.
CIRCUIT CONDITION-RUNNING:
With the FUEL PUMP (FP) operating and Ignition
occurring, the engine should start.
A voltage is induced into the Stator's BATTERY
CHARGE WINDING. This voltage is delivered to the
ENGINE CONTROLLER BOARD (PCB) via Wire 66
to prevent STARTER MOTOR engagement above a
certain rpm.
Circuit board action terminates DC output to the
STARTER CONTACTOR, which then de-energizes to
end cranking and CHOKE SOLENOID operation. The
choke will go to a position determined by the CHOKE
HEATER (CH).
CIRCUIT CONDITION- SHUTDOWN:
Setting the START-STOP SWITCH (SW1) to its
"STOP" position connects the Wire 18 circuit to frame
ground. Circuit board action then closes the circuit to
Wire 18A, grounding the ignition coil. Circuit board
action opens the circuit to Wire 14. Ignition and fuel
flow terminate and the engine shuts down.
CIRCUIT CONDITION- FAULT SHUTDOWN:
The engine mounts a HIGH OIL TEMPERATURE
SWITCH (HTO) and a LOW OIL PRESSURE
SWITCH (LOP).
Should engine oil temperature exceed a pre-set
value, the switch contacts will close. Wire 85 from the
circuit board will connect to frame ground. Circuit
board action will then initiate a shutdown.
Should engine oil pressure drop below a safe pre-set
value, the switch contacts will close. On contact clo-
sure, Wire 85 will be connected to frame ground and
circuit board action will initiate an engine shutdown.
The circuit board has a time delay built into it for the
Wire 85 fault shutdowns. At STARTUP ONLY the cir-
cuit board will wait approximately 6 seconds before
looking at the Wire 85 fault shutdowns. Once running
after the 6 second time delay, grounding Wire 85 thru
either switch will cause an immediate shutdown.
ENGINE CONTROLLER CIRCUIT BOARD
GENERAL:
The engine controller board is responsible for crank-
ing, startup, running and shutdown operations. The
board interconnects with other components of the DC
control system to turn them on and off at the proper
times. It is powered by fused 12 VDC power from the
unit battery.
CIRCUIT BOARD CONNECTIONS:
The circuit board mounts a 15-pin receptacle (J1) and
two single pin terminals (J2 and J3, see Figure 5.2).
Figure 5-3 shows the 15-pin receptacle (J1), the asso-
ciated wires and the function(s) of each pin and wire.
Page 16

Section 5
ENGINE DC CONTROL SYSTEM
Page 17
120V 30A
VOLTAGE
REGULATOR
ELECTRONIC
BY CUSTOMER
NEUTRAL CONNECTION
T2
GREEN
0F
FIELD
CB3
0N
0K
2
2A
22P
44
22S
0N
0N
R1
55
SP - SPARK PLUG
TC - TERMINAL, CONN. 4-TAB
SW2 - SWITCH FUEL PRIMER
CB3 - CIRCUIT BREAKER, 2.5A
R1 - RESISTOR, 1 OHM 25W
GT - TERMINAL, GROUND 4-TAB
LEGEND
BCR - BATTERY CHARGE RECTIFIER
CB1 - CIRCUIT BREAKER, 30A
FP - FUEL PUMP-OR-LPG SHUT OFF VALVE
LOP - SWITCH, LOW OIL PRESSURE
SC - STARTER CONTACTOR
SW1 - SWITCH, START/STOP
IM - IGNITION MAGNETO
PCB - ENGINE CONTROLLER
HM - METER, HOUR (OPTIONAL)
L1 - LIGHT, RUN (OPTIONAL)
HTO - SWITCH, HIGH TEMP. OIL (CLOSES ON HIGH TEMP.)
4
BLACK
6
4
T1
SM - STARTER MOTOR
CH - CHOKE HEATER
F1 - FUSE, 7.5A
4
11S
CB1
11P
33
HM
START
STOP
4
L1
(CLOSES ON LOW PRESSURE)
16
BATTERY
14
15
77
66
J1-14
J1-15
J1-12
J1-13
15
15
J1-11
J1-6
J1-7
J1-8
PCB
14
J3
J2
J1-4
J1-5
J1-1
13
SW2
15
F1
16
RED
14A
14
RED
SC
(OPTIONAL)
REMOTE PANEL
66
66
18
18
0
17
4
3
18
4
WHITE
BROWN
18
14
17
4
REMOTE
PANEL
17
2
2
SW1
66
85
4
17
17
(STOP)
(START)
SC
CS
18A
56
90
IM
85
85
HTO
0B
SP
0
0
0
SM
FP
CH
BLK
CS - CHOKE SOLENOID
0
0
FUEL
PRIME
BROWN
BLUE
RED
FS - FUEL SOLENOID
FS
0
14
Figure 5-1. – Schematic- 4700

Section 5
ENGINE DC CONTROL SYSTEM
Figure 5-2. – Engine Controller Circuit Board
PIN WIRE FUNCTION
1 56 Delivers 12 VDC to Starter Contactor (SC)
while cranking only.
290 Delivers 12 VDC to Choke Solenoid coil
while cranking only. (Two seconds ON, Two
seconds OFF)
3 — Not used.
4 18A Grounds Magneto for Shutdown.
5 — Not used.
6 17 To Start-Stop switch. When wire is grounded
by setting Start-Stop switch to "START",
engine will crank.
7 17 To Start-Stop switch on optional Remote
Panel.
8 — Not used.
9 4 Field Boost DC to Voltage Regulator and to
Rotor windings.
10 66 Starter Lockout. Prevents cranking while
engine is running.
11 85 Fault shutdown circuit. When grounded by clo-
sure of High Oil Temperature or Low Oil
Pressure Switch engine will shut down.
12 0 Common Ground.
13 16 12 VDC Input to Field Boost circuit while
cranking only.
14 18 To Start-Stop switch. When grounded by set-
ting Switch to "STOP" engine shuts down.
15 18 To Start-Stop Switch on optional Remote Panel.
Figure 5-3. – Receptacle J1
In addition to the 15-pin receptacle (J1), the circuit
board is equipped with two single pin terminals (J2
and J3). These terminals may be identified as follows:
1. Wire 14 connects to Terminal J2. During cranking and running,
the circuit board delivers battery voltage to the Wire 14 circuit
for the following functions:
a. To operate the electric Fuel Pump (FP).
b. To energize the Fuel Solenoid.
c. To operate the Choke Heater.
d. To the Remote Wire Harness to operate an
hourmeter or a light.
2. Wire 15 connects to Terminal J3. This is the power supply (12
VDC) for the circuit board and the DC control system.
BATTERY
RECOMMENDED BATTERY:
When anticipated ambient temperatures will be con-
sistently above 32° F. (0° C.), use a 12 volts automo-
tive type storage battery rated 70 amp-hours and
capable of delivering at least 400 cold cranking
amperes.
If ambient temperatures will be below 32° (0° C.), use
a 12 volt battery rated 95 amp-hours and having a
cold cranking capacity of 400 amperes.
BATTERY CABLES:
Use of battery cables that are too long or too small in
diameter will result in excessive voltage drop. For
best cold weather starting, voltage drop between the
battery and starter should not exceed 0.12 volt per
100 amperes of cranking current.
Select the battery cables based on total cable length
and prevailing ambient temperature. Generally, the
longer the cable and the colder the weather, the larg-
er the required cable diameter.
The following chart applies:
CABLE LENGTH (IN FEET) RECOMMENDED CABLE SIZE
0-10 No. 2
11-15 No. 0
16-20 No. 000
EFFECTS OF TEMPERATURE:
Battery efficiency is greatly reduced by a decreased
electrolyte temperature. Such low temperatures have
a decided numbing effect on the electrochemical
action. Under high discharge rates (such as crank-
ing), battery voltage will drop to much lower values in
cold temperatures than in warmer temperatures. The
freezing point of battery electrolyte fluid is affected by
the state of charge of the electrolyte as indicated
below:
15 14
PIN LOCATIONS
J1-1 thru J1-15
J1
J2
J3
1
15
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