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Section 4

ENGINE DC CONTROL SYSTEM

Page 17

VOLTAGE

REGULATOR

TERMINAL BOARD

(TB1)

TERMINAL BOARD

(TB2)

START STOP RELAY

(SSR)

STARTER CONTACTOR RELAY

(SCR)

IDLE CONTROL

TRANSFORMERS

(ICT)

PRINTED CIRCUIT

BOARD

10 AMP FUSE (F1)

LOCATED IN REAR OF CONTROL PANEL

DIODE (D1)

RESISTOR (R1)

CONNECTOR

(C2)

CONNECTOR

(C1)

50 AMP CIRCUIT BREAKER

EXCITATION CIRCUIT

BREAKER (CB2)

10 AMP AUTO RESET

BREAKER (CB1)

BATTERY CHARGE RECTIFIERS

(BCR1 & BCR2)

CONTROL PANEL COMPONENT IDENTIFICATION

Notice to Users of this Manual2
Replacement Parts2
Table of Contents3
Table of Contents4
Generator Fundamentals5
Section 1: Generator Fundamentals5
Magnetism5
Electromagnetic Fields5
Electromagnetic Induction5
A SIMPLE AC Generator6
A more Sophisticated AC Generator6
Section 1: Generator Fundamentals7
Measuring Electricity8
Section 2: Measuring Electricity8
Meters8
The vom8
Measuring AC Voltage8
Measuring DC Voltage8
Measuring AC Frequency8
Measuring CURRENT9
Measuring RESISTANCE9
Section 2: Measuring Electricity10
Electrical Units10
OHM'S Law10
Description and Components11
Introduction11
Engine-Generator Drive System11
THE AC Generator11
ROTOR Assembly11
STATOR Assembly12
Brush Holder and Brushes12
OTHER AC Generator COMPONENTS12
- EXCITATION CIRCUIT Breaker12
- Voltage Regulator13
- Adjustment Procedure13
- CIRCUIT Breakers14
ROTOR Residual Magnetism14
Field Boost CIRCUIT14
Operation14
- Startup14
- ON-Speed OPERATION14
- Field EXCITATION14
- AC Power Winding OUTPUT14
- Battery Charge Winding OUTPUT14
- 10 Amp Battery Charge Winding Output14
Insulation Resistance15
THE Megohmmeter15
- General15
- Testing STATOR INSULATION15
- Testing ROTOR INSULATION15
- Hi-Pot Tester15
Stator Insulation Resistance Test15
- "Testing All Stator Windings To Ground16
- TEST between Windings16
Rotor Insulation Resistance Test17
Cleaning the Generator17
Drying the Generator17
Engine DC Control System18
Printed CIRCUIT Board18
- General18
- CIRCUIT Board CONNECTIONS18
- Dip Switch POSITIONS18
Battery18
- Recommended Battery18
CONTROL PANEL COMPONENT Identification19
Terminal Block20
OPERATIONAL Analysis22
- CIRCUIT Condition - REST22
- CIRCUIT Condition - START24
- CIRCUIT Condition - RUN26
- CIRCUIT Condition - STOP28
- FAULT Shutdown29
- Section 4: Engine DC Control System29
- Troubleshooting Flowcharts30
Section 5: Troubleshooting Flowcharts30
Introduction30
IF Problem INVOLVES AC OUTPUT30
- Voltage & Frequency ARE both High or Low30
- Generator Produces ZERO Voltage or Residual Voltage (2-12 VAC)31
- EXCESSIVE Voltage/Frequency Droop When Load IS Applied32
Problem32
- NO Battery Charge OUTPUT33
- NO 10 AMP Battery Charge OUTPUT33
- Engine will NOT CRANK34
- Engine CRANKS but will NOT START35
Problem35
- Engine STARTS Hard and RUNS Rough36
- Engine STARTS then SHUTS down36
Problem 10 - 10 AMP FUSE (F1) Blowing37
Engine "HUNTS" / ERRATIC Idle38
Section 5: Troubleshooting Flowcharts38
Idle CONTROL "RPM Does NOT Decrease38
Idle CONTROL "RPM Does NOT INCREASE When Load IS Applied38
Problem 11 - UNIT Overspeeds38
Diagnostic Tests39
Introduction39
Section 6: Diagnostic Tests39
TEST 1 - CHECK NO-Load Voltage and Frequency39
TEST 2 - CHECK MAIN CIRCUIT Breaker39
TEST 3- TEST EXCITATION CIRCUIT Breaker40
TEST 4 - Fixed EXCITATION TEST/ROTOR AMP Draw40
Test 5 - Check Stepper Motor Control42
TEST 6 - Wire Continuity43
TEST 7 - CHECK Field Boost43
TEST 8 - Diode/Resistor44
Test 9 - Test Stator45
TEST 10 - Sensing Leads46
TEST 11 - EXCITATION Wiring47
TEST 12 - CHECK Brush Leads47
TEST 13 - CHECK Brushes & SLIP Rings47
TEST 14 - CHECK ROTOR Assembly48
TEST 15 - CHECK Load Voltage & Frequency48
TEST 16 - CHECK Load Watts & Amperage48
TEST 17 - CHECK Battery Charge OUTPUT49
TEST 18 - CHECK 10 AMP Battery Charge OUTPUT49
TEST 19 - CHECK Battery Charge RECTIFIER49
TEST 20 - CHECK 10 AMP CIRCUIT Breaker50
Test 21- Check 10 Amp Fuse50
TEST 22- CHECK Battery & Cables50
TEST 23- CHECK Voltage at STARTER CONTACTOR51
Test 24 - Check Starter Contactor51
Test 25 - Check Starter Motor51
- Conditions Affecting STARTER MOTOR PERFORMANCE51
- Checking the PINION52
- Tools for Starter Performance Test52
- Measuring CURRENT52
- Tachometer52
- TEST Bracket53
- Remove Starter Motor53
- Testing STARTER MOTOR53
TEST 26 - TEST STARTER CONTACTOR Relay (SCR)53
TEST 27- CHECK START-RUN-STOP Switch54
TEST 28- CHECK START-RUN-STOP (Sw1) Wiring54
TEST 29 - CHECK Ignition SPARK55
TEST 30 - CHECK SPARK Plugs55
TEST 31 - REMOVE Wire 18 / Shutdown Lead56
TEST 32 - TEST START STOP Relay56
TEST 33- TEST Wire 16757
TEST 34 - TEST START STOP Relay Wiring58
TEST 35 - CHECK and Adjust Ignition Magnetos58
TEST 36: TEST FUEL SHUTOFF Solenoid59
TEST 37: TEST FUEL SHUTOFF Solenoid Voltage59
Test 38: Check Fuel Pump59
TEST 39 - CHECK Carburetion60
TEST 40 - VALVE Adjustment60
TEST 41 - CHECK Engine / Cylinder LEAK down TEST / COMPRESSION TEST61
TEST 42 - CHECK OIL PRESSURE Switch and Wire62
TEST 43: CHECK START STOP Relay (SSR)62
TEST 44: TEST STARTER CONTACTOR Relay (SCR)63
TEST 45: CHECK Wire 15 CIRCUIT63
TEST 46: CHECK Wire 14 CIRCUIT63
TEST 47: CHECK FUEL SHUTOFF Solenoid63
Test 48: Check Hourmeter64
TEST 49: CHECK Wire 15B64
TEST 50: CHECK Wire 16764
TEST 51: CHECK Wires 11S & 44S64
TEST 52: CHECK Idle CONTROL Switch (Sw2)65
TEST 53: CHECK Idle CONTROL Wiring65
TEST 54: CHECK Idle CONTROL TRANSFORMERS66
TEST 55: CHECK TR1 & TR2 Wiring66
Section 6: Diagnostic Tests67
Test 56: Choke Test67
Disassembly and Exploded Views68
MAJOR Disassembly68
Generator - Figure a70
FRAME, Handle & Wheels - Figure B72
Section 8: Electrical Data74
Electrical Data74
Wiring Diagram 12.5 & 15 Kw (UNITS Without HOURMETER) - Drawing NO. 0E022874
ELECTRICAL SCHEMATIC 12.5 & 15 Kw (UNITS Without HOURMETER) - Drawing NO. 0E0229-A76
Wiring Diagram 12.5 & 15 Kw (UNITS with HOURMETER) - Drawing NO. 0D4609-D78
ELECTRICAL SCHEMATIC 12.5 & 15 Kw (UNITS with HOURMETER) - Drawing NO. 0D6297-A80
- Section 8: Electrical Data81
- Engine Wiring82
Wiring Diagram 17.5 Kw UNITS - Drawing NO. 0G073182
ELECTRICAL SCHEMATIC 17.5 Kw UNITS - Drawing NO. 0G073384
Wiring Diagram, 17.5 Kw MANUAL TRANSFER Switch - Drawing NO. 0G106585
INTERCONECTION Drawing - 17.5 Kw Generator86
Specifications & Charts88
Generator SPECIFICATIONS88
Engine SPECIFICATIONS88
Engine Speeds and Voltage SPECIFICATIONS88
Torque SPECIFICATIONS89
TRIM Torque SPECIFICATIONS89

Brand	Generac Power Systems
Model	4451 & 4986
Category	Portable Generator
Language	English

Generac Power Systems 4451 & 4986 User Manual

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Generac Power Systems 4451 & 4986 Specifications

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