Climate Control Problem/Too much heat
 

I have a 1984 MB 300SD 126 chassis. Heat will not turn off. Disconnecting wire to monovalve does not turn heat off. Whatever position you put the climate control in power remains at monovalve wire. Any suggestions?

Not sure about the 126. Does it have a heater valve? In my 201s, the heat is sign of no vacuum to the heater valve.

Monovalve
 

The monovalve defaults to full heat. It is possible that the solenoid is bad and not pulling the valve shut to restrict the hot water from flowing through the heater core. If the solenoid is activating the rubber diaphram inside the valve could be torn.// It is not too awfully difficult if I remember corectly to remove the top half of the valve-leaving the coolant hoses connected- and inspect the diaphram and bench test the soleniod