2008 S550 (221.186) - experiencing some issues with the A/C cooling well for parts of the day and suddenly reverting to blowing warm air only; sometime powering down the climate control system will eliminate the problem, other times the heat remains. Check of refrigerant reveals a full charge.

Fault code check reveals the following:

9304 A9 (AC comp) - Pressure control valve. Short circuit to ground.


Unable to clear the fault code because the fault is active.

Is the pressure control valve replaceable by itself or does the entire compressor need to be replaced?