Temp control gone crazy!! Help!
 

Hey guys, on my 1991 500SL Ive got a crazy temp control. For several weeks the buttons light up when pressed, but they dont control their function. So if I press AC the AC does not go on, if I press defrost it doesnt go on, etc etc. Sometimes they do work, but usually they dont.

Just this weekend though it really wigged out on me. The temp control shut off, there was no lights or read out on the display, and my car started to surge. I put it in neutral and the engine continued to surge, even up to 3000RPM's. Also I get hot air out of all the vents. I shut the car off and left it alone for a while and now its back to the intermittent temp control, the surging is gone. Im afraid it will come back or will cause damage to the car.

Any help would be much appreciated.

I myself don't have a clue but slsmag posted an interesting cure for an erratic temp control that seems to be an inexpensive fix...

The A/C comes out cold and does not fluctuate, its that when I press the different fan speeds or press to change the flow of air I do not get the intended response. Also the readout on the climate control unit sometimes gets blurred or unreadable.

I think Im going to send the unit to Programa to have it benched. Seems like this is beyond any of the mechanics on the tech forum judging from the lack of knowledge/responses.

I'd be interested in learning how to remove the controller from the dash. I looked at mine when I changed out the radio and I couldn't see how to release it. Special Tools? BTW, these show up on ebay from time to time. Fortunately, mine is OK, but always interested in DIY fixes. Tod

ACC Controller Removal
 

Removing the radio exposes two plastic catches which engage the bottom of the controller at each of its sides. Simply push down on these and pull the controller out.