Section 4 • Troubleshooting
September 2008
4 - 2
T70, T90 & T120 Super Quiet Generator
Part No. 134277
Troubleshooting Guide
The engine/generator set is tested and set at the factory for proper operation in the field. These units
should never require additional adjustments in the field. If needed, adjustments should only be made by a
qualified service technician, otherwise the manufacturer’s warranty may become void.
FAULT
POSSIBLE CAUSE
SOLUTION
No generator output voltage
Circuit breaker tripped
Reset circuit breaker
Voltage regulator
Check voltage regulator wiring
Defective voltage regulator
Replace voltage regulator
Defective Selector Switch
By pass by hardwiring generator
Defective generator
Refer to generator manual
Low generator output voltage
Voltage adjustment
Adjust voltage potentiometer
set too low
Defective potentiometer
By pass or replace
Low engine speed
Call TEREX Service
Loose wire on voltage
Check wiring
selector switch
Fluctuating or surging
Check engine fuel, oil,
engine speed
and air filters
Loose wire on voltage
Check wiring
regulator sensing circuit
Defective voltage regulator
Replace voltage regulator
High generator
Voltage adjustment
Adjust potentiometer
output voltage
potentiometer
High engine speed
Call TEREX Service
