My cabin blower is being crazy and I can't seem to find anything relating to this anywhere.

It will only work with the engine running
All fan speeds work
With the ignition on (engine not running) no blower and no indicator lights are illuminated
A/C hasn't worked for a few months
I can turn the A/C compressor by hand under the hood
System has proper refrigerant pressure
It's a 2001 w/ auto controls

Could it just be a matter of replacing the climate control unit?