Generac Power Systems 4451 & 4986

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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

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