Cause : Rectifier overtemperature comes when the temperature in the rectifier of the power unit has exceeded the permissible temperature limit.

- insufficient cooling, fan failure.
- overload.
- ambient temperature too high.
- line supply phase failure.

1. check whether the fan is running.
2. check the fan elements.
3. check whether the ambient temperature is in the permissible range.
4. check the motor load.
5. check the line supply phases.