I have an update on this problem. My mechanic opened up the glove box liner and checked out the switch over valve. He said all the valves are fine. He showed me that if he disconnected one vacuum line and applied vacuum to it manually with his mouth, the flaps would shut and air conditioned instead of heated air would get to the defroster. He is still working on it, but I just want to clarify what this means. Does this mean that there is a vacuum leak somewhere (if so, where are the common problem areas) or is there some sort of electrical connection problem. I performed another check, in that I checked to see the voltage at the feedback potentiometer and no matter what setting I put the temperature wheel at, the voltage did not change across that part.
Mercedes Maniac, thanks for the link. According to that sheet, I have either an electrical connection problem or a vacuum leak.
1985 190E 2.3-16 Euro