1995 E34 here.

My aux fax wasnt coming on so car was getting hot. It was a fuse which I replaced. It now comes on with the AC. It also kicks in when the car gets too hot. Problem is strange though....

Car with AC on fax position #2 driving in stop and go will get hot to maybe 5/8-3/4. I've turned off ac and the car cools off to 1/2. I've pulled over and stopped and turned off the ac and the aux fan will kick in and cool the car down to 1/2. I've actually done this and turned the ac back on full blast and let the car idle for 15-30 minutes in 95 degree whether with no overheating.

Does that aux fan have multi speeds?

yes it has multiple speeds which is contoled by the resistor pack....which are known to fail. go to realoem.com
and you should be able to look up the resistor pack....I think they are like 25$ or you can call patrick at BMA.
Thats what it sounds like to me but Im sure you might get some more opinions.

Makes sense. I am hoping that is the case as it seems like the car has to nearly overheat to go into high mode.