Terex T90C troubleshooting: 67 symptom-cause-remedy entries from the manufacturer's own service documentation.
Terex T90C — full specs, parts & maintenance.
| Symptom | Cause | Remedy |
|---|---|---|
| No generator output voltage | Circuit breaker tripped | Reset circuit breaker |
| No generator output voltage | Voltage regulator | Check voltage regulator wiring |
| No generator output voltage | Defective voltage regulator | Replace voltage regulator |
| No generator output voltage | Defective Selector Switch | By pass by hardwiring generator |
| No generator output voltage | Defective generator | Refer to generator manual |
| Low generator output voltage | Voltage adjustment set too low | Adjust voltage potentiometer |
| Low generator output voltage | Defective potentiometer | By pass or replace |
| Low generator output voltage | Low engine speed | Call TEREX Service |
| Low generator output voltage | Loose wire on voltage selector switch | Check wiring |
| Low generator output voltage | Fluctuating or surging engine speed | Check engine fuel, oil, and air filters |
| Low generator output voltage | Loose wire on voltage regulator sensing circuit | Check wiring |
| Low generator output voltage | Defective voltage regulator | Replace voltage regulator |
| High generator output voltage | Voltage adjustment potentiometer | Adjust potentiometer |
| High generator output voltage | High engine speed | Call TEREX Service |
| High generator output voltage | Defective automatic voltage regulator | Replace voltage regulator |
| High generator output voltage | Loose wire on voltage adjustment potentiometer | Check wiring |
| High generator output voltage | Neutral binding strap not in place. | Install neutral binding strap |
| Fluctuating generator output voltage | An “ON/OFF” type load may be the cause | Redistribute load if possible |
| Fluctuating generator output voltage | Fluctuating or surging engine speed | Check engine fuel, oil, and air filters |
| Fluctuating generator output voltage | Loose wiring in generator | Check connections |
| Fluctuating generator output voltage | Automatic voltage regulator stability setting may be wrong | Call TEREX Service |
| Fluctuating generator output voltage | Loose wire on the automatic voltage regulator sensing lead | Check wiring |
| Fluctuating generator output voltage | Low engine speed | Call TEREX Service |
| Fluctuating generator output voltage | Engine speed adjustment has slipped | Call TEREX Service |
| Fluctuating generator output voltage | Clogged fuel system | Check for air leaks, clogged fuel filter, kinked fuel line, or clogged fuel pick-up tube |
| Fluctuating generator output voltage | Blocked air intake | Check air filter |
| Fluctuating generator output voltage | Blocked exhaust system | Check engine exhaust system, remove obstructions |
| Fluctuating generator output voltage | Contaminated fuel | Check fuel/water separator and fuel tank for contamination. Replace fuel if needed |
| Fluctuating generator output voltage | Defective governor on engine | Call TEREX Service |
| Low Speed | Defective injectors on engine | Have injectors checked by a qualified technician |
| Low Speed | “Surging” engine speed | Check engine fuel, oil, and air filters |
| Engine turns over (cranks), but won’t run | Unit out of fuel | Check fuel level in tank, fill as needed |
| Engine turns over (cranks), but won’t run | Loose or broken wire in control circuit fuel injection pump solenoid | Check wiring to verify 12V DC is being supplied to the pump solenoid |
| Engine turns over (cranks), but won’t run | Defective solenoid | Replace solenoid |
| Engine turns over (cranks), but won’t run | Clogged fuel system | Check fuel system |
| Engine turns over (cranks), but won’t run | Air in fuel system | “Bleed” fuel system |
| Engine turns over (cranks), but won’t run | Defective fuel pump | Check and replace if defective |
| Engine turns over (cranks), but won’t run | Clogged air intake | Check air cleaner |
| Engine turns over (cranks), but won’t run | Clogged exhaust | Check exhaust system |
| Engine turns over (cranks), but won’t run | Contaminated fuel | Check fuel/water separator and tank for contamination |
| Engine turns over (cranks), but won’t run | Defective injectors | Have injection system checked by a trained technician |
| Engine turns over (cranks), but won’t run | Lost engine compression | Have compression checked by a trained technician |
| Engine won’t crank | Loose battery cable or discharged battery | Check cables and battery electrolyte level. Recharge as necessary |
| Engine won’t crank | Engine “ON/OFF” switch set in “OFF” position | Check switch position |
| Engine won’t crank | Blown fuse in DC control circuit | Replace with 25 Amp. SLO-BLO TYPE fuse if needed. |
| Engine won’t crank | E-Stop | Check to see if engaged |
| Engine won’t crank | Defective starter solenoid | Replace solenoid |
| Engine won’t crank | Defective starter | Replace starter |
| Engine won’t crank | Seized engine | Have engine checked by a qualified technician |
| Engine runs, but loses speed | Unit is overloaded | Reduce load |
| Engine runs, but loses speed | Improper connection | Check or Call TEREX Service |
| Engine runs, but loses power under load | Clogged fuel system air in fuel lines | Check fuel system |
| Engine runs, but loses power under load | Blocked air intake | Check air cleaner |
| Engine runs, but loses power under load | Blocked exhaust | Check exhaust system |
| Engine runs, but loses power under load | Contaminated fuel | Check fuel/water separator and fuel tank for contamination |
| Engine runs, but loses power under load | Faulty governor, defective injectors, or defective fuel pump | Have unit checked by a trained service technician for all of these items |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Oil Pressure Switch Not opening | |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Improper coolant or water mixture | Use a 50/50 mix of water and anti-freeze only |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Overloaded engine | Reduce load |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Broken fan belt | Inspect fan belt and replace as needed |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Defective thermostat or thermocouple switch | Inspect thermostat switch |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Defective water pump | Inspect water pump and replace if needed |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Blocked cooling air inlet or exhaust | Inspect and remove any obstructions |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Defective or grounded temperature switch | Inspect switch and repair or replace |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Defective injectors or injector pump | Have the engine inspected by a trained service technician |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Defective oil pump | Have the engine inspected by a trained service technician |
| Engine shuts down automatically and TROUBLE LIGHT on CONTROL PANEL is illuminated | Defective or grounded oil pressure switch | Inspect switch and repair or replace |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.
Documented causes: An “ON/OFF” type load may be the cause; Fluctuating or surging engine speed; Loose wiring in generator; Automatic voltage regulator stability setting may be wrong. See the table for the matching fixes.
Documented causes: Unit out of fuel; Loose or broken wire in control circuit fuel injection pump solenoid; Defective solenoid; Clogged fuel system. See the table for the matching fixes.
Documented causes: Oil Pressure Switch Not opening; Improper coolant or water mixture; Overloaded engine; Broken fan belt. See the table for the matching fixes.