I purchased an 83 300SD about a month ago and it has 140k miles on it. The problem is the when I turn the rotary dial all the way down to cold position, I still get warm to hot air coming from the center vents. After about 15 minutes on the cold setting it will start blowing cold air. If I move the dial slightly to a warmer setting, I start getting hot air again

Secondly, the blower only works intermittently. It will work when I first start the car up and last for 2-3 minutes. It then shuts off and will come on sporadically for about the same time limit. I've hot-wired the blower and it works fine. I also checked the blower regulator, and when the blower works I saw voltage at the #8 pin and when the blower wasn't working I didn't see any voltage at the same pin. So I've ruled out the blower motor and the blower regulator.

Moving the rotary dial will change where the air blows from, and when the fan isn't working I can here the monovalve cycling and the small inline pump kick on when I hit the defrost button or I turn the dial all the way to hot.

Does anyone think that these problems can be remedied with a new climate control unit?