Terex T120C troubleshooting: 14 fault codes and symptom-cause-remedy entries from the manufacturer's own service documentation.
Terex T120C — full specs, parts & maintenance.
| Symptom | Cause | Remedy |
|---|---|---|
| No generator output voltage | Circuit breaker tripped | Reset circuit breaker |
| Low generator output voltage | Voltage adjustment set too low | Adjust voltage potentiometer |
| Low engine speed | Call TEREX Service | |
| Fluctuating or surging generator output voltage | Check engine fuel, oil, and air filters | |
| High generator output voltage | Voltage adjustment potentiometer set too high | Adjust potentiometer |
| High engine speed | Call TEREX Service | |
| Fluctuating generator output voltage stability | Load may be the cause | Redistribute load if possible |
| Engine won't crank | Loose battery cable | Check cables and battery electrolyte level. Recharge as necessary |
| Engine runs, but loses power under load | Clogged fuel system | Check fuel system |
| Engine shuts down | Oil Pressure Switch not opening automatically and TROUBLE LIGHT on | Improper coolant use a 50/50 on |
| TROUBLE LIGHT on CONTROL PANEL is illuminated | Broken fan belt | Inspect fan belt and replace as needed |
| Voltage does not come up to the rated voltage | Internal problem with the generator end | Check for even reading across the lines, if they are not this would mean you probably have a problem with the wiring of the switch or generator. If the generator voltage reads correctly, contact the TEREX service department. |
| Uneven reading between the legs when applying 24 volts to the field wires | Recheck your wiring connections. After you have the field wire connected start the unit again and check your output voltage. It may still be necessary to flash the fields to restore residual voltage. | |
| Malfunction discovered | Identify symptoms, troubleshoot, perform repair, return to service |
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 tripped. See the table for the matching fixes.
Documented causes: Voltage adjustment set too low. See the table for the matching fixes.
Documented causes: Voltage adjustment potentiometer set too high. See the table for the matching fixes.