F0078 fault in WEG CFW500 Drive indicates Motor Overtemperature via AI/DI. This means an external thermistor connected to the control terminals has detected that the motor is dangerously hot.
Cause:
- Overload on the motor shaft.
- High start/stop duty cycle.
- High ambient temperature around the motor.
- Poor contact or short-circuit (3k9 < RPTC < 0k1).
- Motor thermistor is not installed.
- Motor shaft is stuck.
Remedy:
Check the motor shaft and driven load for mechanical blockages. Optimize duty cycles. Measure thermistor circuit resistances and secure connections.
