Cause : External temperature 1 comes when measured temperature 1 has exceeded warning limit.

The fault code A491 in your ABB ACS880 drive indicates an External Temperature 1 Warning. This signifies that the drive has detected a temperature exceeding the pre-defined warning limit for an external temperature sensor connected to input number 1 (Temperature 1).

1. Check the value of parameter 35.2 Measured temperature 1.
2. Check the cooling of the motor (or other equipment whose temperature is being measured).
3. Check the value of 35.13 Temperature 1 warning limit.