92 325 a/c problem need help

[geladen]

OK, this is a strange one and the Bentley is not much help in this area.
First of, I'm not a novice when it comes to a/c work. I have replaced the condensor, dryer and converted my system to r134 and it has been working fine for the 8years that I have had the car. A few weeks ago my wife told me that the a/c was shutting off every so often. She said it must be something electrical because the lights for the recirculate and a/c buttons turn off and then the air blows warm. I checked it out, put gauges on it and the pressures are fine. I went as far as evacuating the system, put a vacuum pump to it and re-charged it. It worked fine for a few days until it finally quit. The lights don't come on at all. Th eonly light that works on the a/c control panel is the defrost button. I checked the charge and it is fine. I "jumped" the compressor relay and the a/c does blow cold but none of the temperature controls work or light-up.
Could it be the a/c control module? I took it out and even opened it but there is nothing obviously wrong with it or burned. I did notice that after I hooked the control module back up, and started the car with the a/c on, it worked for a few seconds and then the lights went out. Is there anything else that gives the control module any kind of signal that shuts it down? I'm leaning towards the control module, I know they are a problem in the newer digital models but what about these? I would hate to buy a new one and the problem is elsewhere. Is this something that can be diagnosed with the dealers computer?
Any help or ideas will be appreciated, it's getting hot in Florida...
thanks

[geladen]

No one has had this problem? It's driving me nuts!
I have checked everything... I'm going to try the hi/low switch but I doubt it's the culprit. Here is the odd part, if I unplug the control module and plug it back in, A/C works for a few seconds, 15 to 20, I can hear one of the motors in the dash moving flaps or whatever, and then the lights go off, snowflake and recirc, and compressor disconnects....
Arghhh
I'll keep messing with it tomorrow.
Kris

[Jeron]

On the E46 the ac system runs a self diagnostic every 10 starts or so where it actuates every element(flapper etc.) of the system. E36 may have the same thing and by completely disconnecting it you are resetting and causing a diagnostic cycle.

Although you claim to be a novice, I think your level of experience on your ac has surpassed most of us here. The best I can do is BUMP your thread.

Good luck

[blkongry]

All I can offer is that I had my expansion valve replaced last year on my '94 with the dual climate control system. I knew it was the expansion valve, but in talking to the tech at the shop, he said these 'climate control' systems can be very finicky and quirky. He said he's seen some strange things happen with them and repairs can be as much as $3K (I'm guessing that meant for a full replacement). I personally would rather have the simple hot/cold selector and fan rather that individual climate control systems.

It definitely sounds like your control system is dying/dead. It may not even be 'sensing' anything and kicking it out... it could be an electronic part that is just failing and triggers the system to shut off. Electrical circuitry can burn out and fail without any outward signs. I have a feeling you'll go nuts trying to track down the problem, and unless you are exceptionally skilled at a electronic diagnostics, you are probably better off trying to find a used replacement climate control system.

[blkongry]

May want to try contacting this guy... he's got good feedback and seems to know his stuff. You can find help in the strangest of places... http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7965804176&category=33545&sspagename=WDVW

[geladen]

Originally posted by Jeron
Although you claim to be a novice, I think your level of experience on your ac has surpassed most of us here...

Thanks for your vote of confidence, after all I'm not really a novice, I'm an aviation mechanic turned graphic designer, and my dad owned a Volkwagen shop that I ran for a few years. Plus it helps that my brother is an air conditioning contractor. Anyway, I took the car down to a shop and had it scanned for codes. Even the 92 with the rotary knobs has a self diagnosing feature and it ties into the ECM. After scaning it came back with the eveporator temperature sensor being bad. Of course it's a dealer part so I'll get it from the local dealer tomorrow and try it.
Ill post my results tomorrow. If that's not it, Ill be going back to the shop to see what else we can do with the scanner. That scanner is so cool, it even tell you if the switches are turning on or off, reads all the different temperatures from the various sensor and wether the mixing valves are opperating or not.
later
Kris

[geladen]

Well, that was it! The evaporator temperature sensor fixed the problem.
Apparently if the module senses that the temp. sensor is not operating, it shuts down the system, go figure. Unfortunately the Bently only gives resistance values for the heater core temp sensors but not the evaporator's. Cost me $60 and of course it was a dealer item.
Anyway for those interested, here is the part number. 64.51.1.468.411.
It's relatively easy to do, it's on the passengers side and once you take the bottom panel, the knee "buster" and the lower heater duct out, it slides right out of the evaporator. I have picts if any-one is interested.
Cheers
Kris