Cummins/Onan WC Series troubleshooting: 13 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan WC Series — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Cause | Remedy |
|---|---|---|
| Alternator fails to charge or puts out low or unstable charge rate | Alternator belt loose. Loose or dirty battery connections. Worn or defective brushes. Faulty regulator. | Tighten belt. Clean and tighten. Replace brushes. Replace regulator. |
| Excessive charging rate (Battery requires too frequent filling) | Tighten connections, | |
| Generator will not build up voltage. | Circuit breaker in 'off' or 'tripped' position | Reset and close breaker |
| No AC power to Magneciter | Check AC voltage at E1-E2 with the plant operating. Voltage should be five percent of the rated voltage. If not, check continuity from E1-E2 back to generator | |
| Partial loss of residual in Rotor | With plant operating, jumper from E2 to heat sink of field rectifier Z until voltage begins to build-up. Then remove. | |
| Output voltage slow to buildup. | Circuit breaker opens in about five seconds | |
| Output voltage slow to build up and five percent below rated voltage after build up. Voltage regulation poor. | Either Field Rectifier W or Z shorted | Test rectifiers and replace if defective |
| Output voltage slow to build up and higher than rated voltage after build up | Open circuit in one or more Control Rectifier | Test rectifier and replace if defective. Check soldered connections to rectifiers |
| Output voltage slow to build up and ten to twenty percent above rated voltage after build up | Open in one Field Rectifier or Open circuit in Gate winding G1-G2 of Reactor A or B | Test rectifiers and replace if defective. If Field Rectifiers Y and Z check okay, check continuities of Gate windings G1-G2 |
| Output voltage builds up normally but less than rated voltage after build up | Shorted winding in Control Reactor | Test Control Reactor and replace if defective |
| Output voltage builds up normally with slightly less than rated voltage at no load and low voltage at full load | Compound winding S1-S2 installed backward or has open circuit | Check wiring diagram for polarity of compound windings through Reactors A and B and test for continuity |
| Output voltage builds up normally but 20-percent above rated voltage after build up. Voltage regulation poor. | Compound winding S1-S2 installed backward through one Reactor (A or B)) | Check wiring diagram for polarity of Compound winding through Reactor A or B |
| Output voltage builds up normally but is twenty-five percent above rated voltage after build up | Open circuit in Control Rectifier bridge | Check continuity from the junction of Control Rectifiers W and X to the junction of Control Rectifiers Y and Z |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Alternator belt loose. Loose or dirty battery connections. Worn or defective brushes. Faulty regulator.. See the table for the matching fixes.
Documented causes: Circuit breaker in 'off' or 'tripped' position. See the table for the matching fixes.
Documented causes: Circuit breaker opens in about five seconds. See the table for the matching fixes.