My 87 190D 2.5 N/A has all the classic signs of a feedback Potentiometer failure, but I am confused as to its role concerning temp regulation, so here are a couple Q's 1) Is there temp regulation when the Demist (RH Upper button on CCU) is pushed? 2) How about Defrost? (far left, bottom row) 3) Will Faulty vaccum pots lead to erronious temp regulation? (ie center door not getting in the right place for a given mode) 4 Can an improper volatage signal from the Feedback Pot. PREVENT the compressor from coming on when the Demist button is pushed? True for max selected on the Temp Wheel? I was under the impression that the Volt signal from the Feedback Pot. is disregareded in max temp setting? Thanks! Scott