AC failure diag help

[Overboost]

Originally Posted by Bdc101

Thanks all for the quick responses.



I started the car, pulled the plug out of the pressure switch, and nothing changed (with the AC button on or off). I didn't have a second person to help me so I couldn't watch it while the car was starter, but I'll try that later today.



I did double check that the pressure switch was not physically damaged, and the connector was plugged in solidly.



Would this indicate a bad aux fan then? Where does it say that the aux fan has to be running for the AC compressor to start?

My aux fan failed and my A/C would not engage the compressor clutch. Mine is a 2004 M54 so I cannot be certain other models are the same. Once I replaced my fan, everything worked again. This is where a Foxwell would help as you could simply command the fan to run to check the fan operation. Whether or not this is your entire AC issue, you need that fan in the summer months on the 3.0L M54.