Cummins/Onan WC Series troubleshooting: 17 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 unsteady charge rate | Alternator belt loose | Tighten belt |
| Alternator fails to charge or puts out low or unsteady charge rate | Loose or dirty battery connections | Clean and tighten |
| Alternator fails to charge or puts out low or unsteady charge rate | Worn or defective brushes | Replace brushes |
| Alternator fails to charge or puts out low or unsteady charge rate | Faulty regulator | Replace regulator |
| Excessive charging rate (battery requires too frequent filling) | Loose connections on alternator and regulator | Tighten connections |
| Excessive charging rate (battery requires too frequent filling) | Faulty regulator | Replace regulator |
| Noisy alternator | Defective or badly worn belt | Replace belt |
| Noisy alternator | Misaligned belt or pulley | Align properly |
| Noisy alternator | Loose pulley | Tighten pulley |
| Noisy alternator | Worn bearings | Replace bearings |
| Generator will not build up voltage | Circuit breaker in "off" or "tripped" position | Reset and close breaker |
| Generator will not build up voltage | Open in circuit breaker | Stop plant and check breaker continuity |
| Generator will not build up voltage | 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 |
| Generator will not build up voltage | 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. |
| Generator will not build up voltage | Pair of field rectifiers (either W & Z or X & Y) open | Test rectifiers and replace if defective |
| Output voltage slow to buildup. Circuit breaker opens in about five seconds | Both field rectifiers X and Y shorted | |
| Output voltage slow to buildup. Circuit breaker opens in about five seconds | Either field rectifier X or Y shorted |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Circuit breaker in "off" or "tripped" position; Open in circuit breaker; No AC power to Magneciter; Partial loss of residual in rotor. See the table for the matching fixes.
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: Defective or badly worn belt; Misaligned belt or pulley; Loose pulley; Worn bearings. See the table for the matching fixes.