Vintage Cars: 1976 450sl heater, vacuum line, heater valve

Question
I purchased a 1976 450sl around the first of the year ('09). We have been going through it and repairing what is necessary. Now that it is summer the heater has become a problem. It is on all the time. Do you know how to fix it or can I disable it for  the summer months? Fixing would be preferable if not too difficult or costly.

Answer
on the drivers side  fire wall you will see a vacumm pod that has a lever on it. That lever should connect to the heater valve, just push the lever in the opposite direction and should close coolant into heater core.  Your fix may be vacuum line, or a new vacuum pod
Some 76 models had the dreaded servo that controls the heat, if that is the case on yours email me back and I will walk you through that fix
Good Luck
Ron