Air Conditioning not working, middle of summer, PLEASE HELP

[joeman237]

My 93' BMW 325is (E36)'s air conditioning has been malfunctioning for about two weeks now and I can't figure out why. I have replaced the AC the computer, but still have the same problems. The problems is all of the lights on the buttons are stuck on, and none of them will toggle at all. The blower control still works, and the foot/head/defrost selector still works, but I cannot turn on the AC, Recirculation, and Rear defrost. I have looked all over online, all of them either say replace the AC computer (which I did), or replace the final resistor or control on the blower motor, but I know it isn't that because the fan still works, it just blows air from outside.

[MarcoZandrini]

Did you replace the hvac computer with a new or used computer? Is the car having any other electrical issues? Have the electronic in the dash been modified (e.g., an aftermarket head unit)?

[joeman237]

I bought this car used at a dealership, but I am unaware of any electrical modifications. The AC computer that I bought, which I am assuming is what you're referring to as the HVAC computer was used off a 1996 BMW 318i convertible. The only other electrical problem is that the sunroof never wants to open, and I was thinking it might be the comfort relay, but I am not positive about that. I was, however, suspicious of the car that this computer came from, because I know that many of them have digital control panels, but mine has the old manual style AC Control. I also read somewhere that the AC is stuck in a sort of "limp mode" where the AC isn't handled by the HVAC, rather is stuck in a mode where everything kind of works (like the defrost working, but very slowly), but the AC/Heat doesn't work at all.

[marknfw]

I'm having a very similar, maybe the same problem. All the controls on the AC just randomly do what they want to. Sometimes it blows cold air, but sometimes, like today, it blasts the heater, which is not cool in the Texas summer! I see that Marco asked about any other electrical problems. My radio has also started having a problem, it comes on and I can change stations, but the volume knob does nothing. I really don't think they are related, as the radio thing started much later than the AC thing, but I guess they could be. Help! What is the AC computer and how hard is it to change on a 1999 328i?

[joeman237]

Finally, I figured out what was wrong with my AC, after a long night of tracing wires I finally found the problem. Apparently there is a computer grounding wire that came off of the wiring harness. The wire is located right above the gas pedal of the driver's side dash if you take of the cover. It was literally just a wire!!!!. I have replaced my original stereo with an upgraded pioneer sound system so sadly I cannot tell if it affected the radio

[marknfw]

This is what I ended up trying for my problem. Worked like a champ! Spent about $30 on soldering equipment and $1.50 on a couple of capacitors and once again I can handle the Texas heat!

http://www.macadamizer.com/bmwfix.html