I have an '85 928s. The fan know broke so I bought a new climate control module, installed it, and now I'm getting a feedback whine coming from who knows where. I had to pull the a/c fuse to be able to drive it anymore. Any ideas???
Also, the old units' light didn't work (believe it or not, I didn't know it lit up!).

 

That's fan ****......sorry!

 

i could be mistaken but, but it sounds like your talking about the little fan behind the inside air temp sensor. if so when you installed the climate control module you bumped it and it is now making contact with the trim. remove the climate control module again and you will see it touching something

 

You may have disturbed the ground wire to your stereo. Check that while you're at it.