Danfoss · VLT AutomationDrive FC 301/302
The drive's protective function has detected an issue with the external fan, indicating it is not running or improperly mounted. For DC fans, this occurs if no feedback is received from its sensor when commanded to run. For AC fans, the voltage supply is monitored.
Click steps to track your progress.
Safely de-energize the drive and visually inspect the external cooling fan blades for obstructions (e.g., dust, foreign objects).
With power off, manually attempt to spin the fan blades to check for mechanical binding or seized bearings.
Verify the external fan's power supply connections (e.g., L1, L2, L3 on X301 for AC fans, or +24V, GND for DC fans).
Measure the voltage supplied to the external fan terminals (e.g., 230VAC for AC fans, 24VDC for DC fans).
If the fan is a DC type, measure the feedback signal line (e.g., terminal 18) from the external fan connector to the drive's control input.