So my a/c head unit started flickering last fall, and then the A/C stopped working. I bought a replacement head unit and had a local shop program it, but I still don't have A/C! I replaced the FSU to no avail. I can feel cold air being forced into the cabin at highway speeds but the blower does not blow anything at all. Aux fan doesn't turn on at all, but it does appear to want to turn on if I detach and then reconnect the power connector. Will replace it soon.
Where should I begin troubleshooting? Are the Aux fan and blower be connected? or do I have two separate issues?
edit: the car is a 2001 540i Wagon with ~120,000 miles