Quote Originally Posted by Adnan
Hi,

I had the exact same thing happen on my '91 535i so I pulled out the ETM and started to go through the schematics. There was only one possible culprit, based on what I could tell. Are you ready for this - it was the airconditioning pressure switch.

The simple yes/no test is to unplug the wiring to that switch and see if the fan stops. If I recall correctly, the switch fails to a short. An easy test with zero cost and about three minutes invested. I did that and can also confirm that the switch I removed was a dead short.

I had to evacuate the system first since removal of the switch will dump all of that R12. The switch is located under the washer fluid reservoir and is pretty easy to unscrew. I installed a new switch and the problem was completely cured.

Good luck,
Adnan
I didn't think about that. That reminds me to test that switch. I would guess mine is long since dead due to my air not working.

BTW, isn't there a schrader valve where that switch screws into? If so, you wouldn't need to dump the entire system, just unscrew it. Let me know if you remember or not. I'd like to be able to change it without dumping the system.

Thanks!