My friend's '85 280SL has the dual climate control with individual temp wheels for each side of the car. Neither side of the car gets much heat regaardless of what position the controls are in. It gets warm at first but cools down when the blower is switched on. The temp gauge is in Centigrade and runs at about 65-70 degrees C. Is this a normal operating temp or is it too cool? If this is too cool, are thermostats available in different temps? How much is an original MB thermo? Thanx for any help!