Cause : Overtemperature heat sink AC inverter comes when the temperature of the power unit heat sink has exceeded the permissible limit value due to insufficient cooling, fan failure, overload, ambient temperature too high, pulse frequency too high.

- check whether the fan is running.
- check the fan elements.
- check whether the ambient temperature is in the permissible range.
- check the motor load.
- reduce the pulse frequency if this is higher than the rated pulse frequency.