I was afraid you were going to say that.
I know this '80 is a different beast climate control wise. As you stated I do get air flow out of the center vents throughout the entire cycle of the temp wheel. It will only stop flowing air if I push the selector button for defrost. The symptoms of the system failing a few nights ago was that it would not send heat to the side ducts or floor unless I cycled the defrost button first for a few seconds then pushed either the fan hi or low button. At this point the center vents would remain close and I would get heat somewhat as normal but flow seemed somewhat decreased coming out. Now as I have said, I get no heat regardless of setting, ie. defrost or heat mode. Is it at all possible that the temp wheel selector is defective not causing a difference in resistance between it and the sensor? I'm trying to understand the operation of this sytem through the cd info etc. but can't seem to find a starting point at which to start testing from.
Have you got any ideas to start the process of elimination for part failure?
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan