Help!! My Heater Will Not Turn Off In My 81 300 Sd...
 

AND I CANT DRIVE IT ,IT HAS EVEN STARTED TO WARP THE DASH ITS SO HOT ,ANY HELP WOULD BE GREAT I DONT WANT TO HAVE TO DISCONNECT THE HEATER.

Your heater/AC servo is probably stuck and not turning off the hot water to the heater core.

That happened to me in 2 of my 300SDs. One I replaced the servo (~$400) and the other (old beater) I put in a manually operated valve ($0).

Take your choice.

P E H

Monovalvitious?
 

Does the 81 126 have a monovalve?

http://mbdieseldiy.tripod.com/monovalve.htm

You have a monovalve. If it is stuck open, you get heat all the time. However, it can also be the pushbutton control unit holding it open.

You pull it very easily -- two or four self-tapping screws and it just pulls out. If the rubber bellows is bulged or cracked, put a new one in. They tend to stick if the bellows swells, and when it breaks, the plunger in the solenoid locks in place, usually open.

Peter