11-8
OVERVOLTAGE – FAULT CODE 12
WARNING
Some genset service procedures present hazards that can result in severe personal injury
or death. Only trained and experienced persons with knowledge of fuels, electricity, and machinery
hazards should perform genset service. See Safety Precautions.
Logic: Instantaneous Fault – AC voltage S1–S2 greater than 150 VAC
Delayed Fault – AC voltage S1–S2 greater than 138 VAC, but less than 150 VAC for 3 continuous minutes
Possible Causes: Genset loads, Inverter/Charger, wire connections, AC sense transformer, windings
Diagnosis & Repair:
1. Verify that Last Fault is FC 12: Yes, continue diagnosis; No, troubleshoot actual last fault.
2. Measure AC voltage.
3. Measure AC frequency while changing engine rpm to determine if frequency response matches engine
rpm response: repair damaged generator drive system as necessary.
4. Cycle loads to determine if a particular load causes fault: diagnose faulty load as necessary.
5. Determine Inverter/Charger battery charge rate (typical default is 80 percent): if adjustable reduce to 30
percent.
6. Verify balanced loads in 120/240 VAC applications: balance loads within 10 percent line–to–line as re-
quired.
7. HGJAD only – Run genset in Engine Run Only mode and externally excite field F1–F2 with 12 VDC or
24 VDC and measure main and quadrature winding AC output.
8. Non EFI – If the genset will not stay running measure genset frequency, quadrature winding and main
winding voltages using Break-Out Tool 420–0603 and Instruction Sheet R1098.
9. Remove connector P1 from control and re-install and try to start genset: inspect, repair or replace P1 con-
nector pins as necessary.
10. Measure field, quadrature and main winding resistance: clean slip rings, replace brushes, repair harness
and replace rotor or stator as necessary.
11. Measure field, quadrature and main winding resistance to ground: clean slip rings, replace brushes, re-
pair harness and replace rotor or stator as necessary.
12. Measure field, quadrature and main winding resistance to each other: clean slip rings, replace brushes,
repair harness and replace rotor or stator as necessary.
13. Check brush alignment per PSB-682a.
14. Dealers contact Distributor for technical support, Distributors contact factory for technical support.
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