AC not working

Not very familiar with BMW but many cars will shut down the air conditioning if it sees engine over heating conditions or gets an eronious signal that the car may be over heating. A/C takes power from the engine and the theory is cancelling the a/c in overheat conditions will allow th engine to run a little cooler.

Have your auxiliary fan checked. It may have gone bad. You may also want to have your fan clutch checked. Both of these things went bad on my BMW and I had trouble with the engine temp getting high AND my air-conditioning would barely work...

I had this same problem and it was simply the fuse for the auzilary fan. Check your fuses under the hood.