I have the above mentioned Mercedes. I had as situation a few years ago where the heat would not turn off. I went to look at the heater control valve and unplugged it and pluggedit back in, and everything worked okay.

Well I think that I have run out of luck as I tried that yesterday and that did not work. So at this point I need to determine where the problem is. Is it the switch, heater control valve, vaccume line or?

Any ideas on this? Thanks, Nick