Cummins/Onan PX12000 troubleshooting: 47 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan PX12000 — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Symptom | Cause | Remedy |
|---|---|---|
| Starter won't run | Low battery | |
| Starter won't run | Blown fuse | |
| Starter won't run | Incorrect or poor connection of wires | |
| Starter runs, but Engine won't start. | Deteriorated fuel | |
| Starter runs, but Engine won't start. | Fuel piping clogging | |
| Starter runs, but Engine won't start. | Clogging of Air cleaner | |
| Starter runs, but Engine won't start. | Low oil level | |
| Starter runs, but Engine won't start. | Faulty spark plug | |
| During operation Rotation decreased | Deteriorated fuel | |
| During operation Rotation decreased | Fuel piping clogging | |
| During operation Rotation decreased | Clogging of Air cleaner | |
| During operation Rotation decreased | Clogging of Cooling air intake | |
| During operation Rotation decreased | Low oil level | |
| During operation Rotation decreased | Faulty spark plug | |
| Unstable rotation | Deteriorated fuel | |
| Unstable rotation | Fuel piping clogging | |
| Unstable rotation | Clogging of Air cleaner | |
| Unstable rotation | Faulty spark plug | |
| Unstable rotation | Incorrect or poor connection of wires | |
| Breaker turned off | Overload by connected appliance | |
| Breaker turned off | Incorrect or poor connection of wires | |
| Breaker turned off | Insufficient capacity of extension cable | |
| Breaker turned off | Leakage | |
| Carbon brushes are excessively worn | Overload by connected appliance | |
| Carbon brushes are excessively worn | Incorrect or poor connection of wires | |
| Carbon brushes are excessively worn | Insufficient capacity of extension cable | |
| Low Engine Power/AC Output | Overload by connected appliance | |
| Low Engine Power/AC Output | Incorrect or poor connection of wires | |
| Low Engine Power/AC Output | Insufficient capacity of extension cable | |
| Low Engine Power/AC Output | Carbon brushes are excessively worn | |
| No AC output | Exciting coil insulation NG (PX12000) | Replace exciting coil with new one |
| No AC output | Brush and slip ring of rotor insulation NG | Replace brush and slip ring with new one |
| No AC output | Stator winding resistance between terminals faulty | Replace stator with new one |
| No AC output | Stator insulation resistance NG | Replace stator with new one |
| No AC output | A.V.R. insulation NG (PX12000) | Replace A.V.R with new one |
| No AC output | Diode unit and C.T. insulation NG (RGV13100T) | Replace diode unit and C.T with new one |
| AC Voltage is too high or too low | Engine speed too high or too low (nominal engine speed at no load; 3,700 to 3,750 rpm) | Adjust to the rated rpm |
| AC Voltage is too high or too low | Stator winding resistance and insulation faulty | |
| AC Voltage is too high or too low | Rotor resistance and insulation faulty | |
| AC Voltage is too high or too low | Idle control unit insulation NG (PX12000) | Replace idle control unit with new one |
| AC voltage is nominal at no-load, but load cannot be applied | Engine speed is low | Adjust to the rated rpm |
| AC voltage is nominal at no-load, but load cannot be applied | Generator is overloaded (total wattage of appliances connected to generator) | Reduce the load to the rated output of generator |
| AC voltage is nominal at no-load, but load cannot be applied | Appliance faulty | Replace it |
| AC voltage is nominal at no-load, but load cannot be applied | Engine is overheated; generator cooling air inlet and/or outlet is clogged with dirt, grass, chaff or other debris | Remove it |
| AC voltage is nominal at no-load, but load cannot be applied | Insulation of generator faulty | |
| Engine does not run — Electric starter does not operate | The key switch (or remote switch) is turned to "START" within 2 seconds the engine has been stopped | Wait for more than 2 seconds and then turn the key switch to "START" position |
| Engine does not run — Electric starter does not operate | No fuel in the tank or the fuel cock is closed; the remote controller is connected | Both the key switch of the generator and the switch of remote controller must be turned to "ON" position |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: Deteriorated fuel; Fuel piping clogging; Clogging of Air cleaner; Clogging of Cooling air intake. See the table for the matching fixes.
Documented causes: Exciting coil insulation NG (PX12000); Brush and slip ring of rotor insulation NG; Stator winding resistance between terminals faulty; Stator insulation resistance NG. See the table for the matching fixes.
Documented causes: Deteriorated fuel; Fuel piping clogging; Clogging of Air cleaner; Low oil level. See the table for the matching fixes.