Good Day Gentlemen, I have a 1991 300e with about 155k miles on it that my college age son drives. I try to do most of the maint. on it myself. I changed out the blower motor a couple of years ago {way easier than my 240 Volvo} but just recently the climate control just stopped working alltogether. No matter what button is pressed nothing happens. So I searched old postings and checked all fuses and ended up at the three wire connector in back of the master cyl. booster. Now when I check for power here I get 12v on the red but no voltage from any other wire. When I jumper red to yellow the fan comes on and runs great at high speed defrost. I can not change the air flow with any of the buttons on the climate control unit. My question is , do I just change out the climate control unit or could I have another problem like a vacuum leak, I thought I heard a whistle like sound coming from the back of the climate control shortly before it stopped working. Cheers, Michael

 

Michael
good luck on this one. i have been battling this problem for a couple weeks now. mine stopped altogether also. gonna try to find a replacement climate control and see if there is any change. hate to diagnose this way but havnt found any other useful info.
martin

 

I have a 1993 300E and the climate control recently began working intermittently. It's more not functioning, than it is functioning. Have either of you been able to figure out the problem yet? How easy is it to access the blower motor? It's my first Mercedes and it is in very good shape and would like to keep it this way.

 

Did you mean the air-conditioner worked intermittently? If so, it could be due to a defective air-conditioner compressor relay, or poor contact between the relay and the socket. If the air-con does not work, unplug the replay and put it back and see if the air-con works properly. The relay is behind the car battery, with Parts No. 002 545 13 05 shown on the case cover.

 

Located the problem. The metallic strip "fuse" located under the hood between the hood alarm button and strut anchor was severed, from age. I installed a aftermarket fuse block and sovled the issue.
Thanks for the help.