HVAC Issues

[yukon101]

Yesterday I thought it would be a great idea to take the control panel (the one below the OBC and radio) to do some cleaning, I get it all apart (wearing anti-static wrist band) and found I had a dead bulb and I thought no biggie and I un-solder it. I try and LED in it then found out it was 12V power, shoot. I leave the light out put it all back together and put it in the car, I turned it on and the fan was always on even when turned "off" and didn't adjust unless it was set to max, another no biggie to me. I get in it in the morning turn it to hot since it was chilly and got great heat out of the drivers side but not passenger, this afternoon I get in it and turn it to the cold and push the AC button. I drive a little and it doesn't cool down, on my way home it was as hot as it was in the morning and acted as though I never touched it (passenger lukewarm). What could cause this?

[XAlt]

Nothing or Max is the sword, blown MOSFETs that do the job of a resistor. Split heat is a symptom of a stuck control valve (two valves in the box, one for each side of the cabin) in the engine bay, probably time to clean it out.

Did you get the fluid changed out on your trans btw?

[yukon101]

What MOSFETs should I get that are still purchasable (just about all the old posts I found didn't stock them anymore)? I took the entire IHKA out from behind the heater box and found it had four cracked solder points that I have now fixed, maybe that could have been the AC issue and in addition to the valves? I just thought it was weird for it to spontaneously go out right after I put it back in. Unfortunately I have haven't had the money to change the trans fluid as the water pump decided to leak all over the next day. But on the bright side the previous owner dropped off a giant binder containing the third valet key, original window sticker, dealer brochure, and everything ever done to the car. I then found the trans fluid has been changed at least 3 times and has had a new valve body since 150k for shifting issues also.

[shogun]

E32Fan mentioned here some specs https://www.bimmerforums.com/forum/s...hlight=mosfets

[XAlt]

http://bmwe32.masscom.net/johan/wate...tervalves.html

[youngbimmer]

It may be the actual control unit needs refurbishing....about to send mine to ProGrama because I'm sick of reflowing the thing and just wanted rebuilt. I replaced my heater watervalves with brand new OEM Bosch unit, and it was not an improvement. Hot on my drivers side, cool (but not cold) on the passenger side.

[yukon101]

My initial thought was that the control unit wasn't talking at all to the rest of the system but when I hit the AC button it engages the secondary fan as it should and the fan would change to high. I guess the next step would be to check the heater valve to see if it is trying to disengage but cant (it worked fine before the water pump went out). I found the new MOSFETs for $2/each plus $10 shipping (why cant everything just be amazon prime). Any input from anyone as to check?

[shogun]

Heater valve testing http://www.bimmerboard.com/forums/posts/841827/

[yukon101]

You guys are a great help moving from my relatively simple GM Northstar (Olds Aurora) to this rather complicated amazing automobile. If I understand correctly 12v closes the heater valves while no voltage opens them? I should really learn more German and make this easier on myself.

[shogun]

yes, no power = valves open, with 12 V pulsating, valves close accordingly.
In case you understand a bit German, here is a training manual for the IHKA, even if you do not understand all the German tech info, the drawings and pics help, best is you download it, see under heating and airconditioning http://www.e38.org/e32/
wiring diagrams are also there in that link
Then here the shop manual https://www.bmwtechinfo.com/repair/main/

[yukon101]

Apparently my radio died so I popped the hood and checked the fuse box, I found a blown fuse staring me in the face and what do I see? Its HVAC fuse number 20 I think, excitedly I jump back in the car and the fan works as it should and I stopped having heat blown in my face and got cool air again and my DIC (GM for driver info center) suddenly lit up again too. Who knew a little 7.5 amp fuse could cause such trouble. Next issue to solve is less airflow out the driver side vents vs the passenger. When I had both the covers off the 4 motors that were accessible were fully seated and everything.

- - - Updated - - -

Come to think of it I think I accidentally blew the fuse while I was testing the lights for the control panel. By accident trying to pry the connector off I jumped 2 of the pins on the 3 wire connector and saw a small arch and the fan kicked on.