Question on 79 450SLC
 

After four months I finally have heat and Ac, vacuum leaks electric trouble and and the servo being rebuilt twice, ( both times at no cost). Now I have another situation. The servo is no parking when the off button is pushed, this is a 3nd generation system by the way. It seems it only happens when the car is cold. Over the weekend as I said I had heat, but it wasn't terrific. I evacuted the vacuum system from the ACC from the source. Check valve 93 I believe it was. I started up the car and after a while I got plenty of heat. Why this worked I don't know, but someone suggested I do this. That is when the servo wouldn't park, but when the car warmed to operating temp it shuts down fine. One thing I found yesterday, actuall two. When I turn on the system I hear clicking behind the dash in the area of the glove box. Also, if I play with the ignition key and turn to a certain point, which seems to be between position 2 and start the servo parks, but the point of contact is so small if I just touch the key the servo runs. Also, I notice when the car is warm and heating well, if I put a load on the engine the system shuts down until the load is off. Finally in all the above, if I reve the engine to 2000K the servo will park when the off button is pushed. However once in awhile it restarts, and I go back to 2000K and if finally parks, this is not unusally for these systems I have read. One article I read said to turn of the system before you stop the engine and it is reving above 2000K

One person suggested the electrical part of the ignition, that is the part the ignition switch is plugged into behind the dash is not working correctly and probably needs to be fix. He concluded as the other functions are working on the ignition, it is a plastic piece in the electrical connection that needs to be replaced.

Another person suggested I have a hugh vacuum leak, but I had a experience mercedes mechanic fix a couple and last friday he check the system and couldn't find a leak.

I spoke to the rebuilder of the servo who has worked on these system for many years and he thinks it is in the ignition.

Anyone every experience this type of problems? I have replaced two of the 3 check valves that go into the drivers door. I also replaced some rubber vacuum splitters which were old and IMHO need replacement. At least now the window go up and down a bit faster then before. I also cehck the vacuum bottle and the manifold connection where the vacuum is produced all checked out OK Thanks@