Ok all you climate control wiring gurus

There I was trying to figure out why I was not getting heat in my '81 300TD. The circulator pump was running and the heat valve was opening and closing
when I had the temp to hot and was pulling its connector off and putting it back on. But, still no heat.
Then, I noticed a black wire in the same sleeve as the wires going to the heat valve that went past the valve and into the depths of the engine compartment. I followed this wire and found an alligator clip on the end of it that was attached to a bracket mounted to the engine (apparently for a ground). If I unclipped this wire from the bracket, all of a sudden I started getting heat in the car. If I put it back, the air started cooling down.
So, I now have heat, but have a wire not attached to anything to make it happen. The temp control in the car appears to still work, as moving it toward cold will allow the air to cool down.
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an open circuit in the sensor chain (in-car, ambient, temp wheel) causes the system to go to full heat. Bill Ditmire Ditmire Motorworks,Inc. 425 White Horse Pike Absecon,NJ 08201 http://www.ditmire.com 609-641-3392
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It's not going full heat though. It seems to work as advertised as long as I keep this wire disconnected.

cooling
the
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Well, the story I got from the previous owner was the mystery wire was used to 'jump' the climate control when it died. He said the wire is no longer needed since I replace the control unit, but no one is able to tell me exactly what might have been jumped because it never worked right until I changed the climate control and disconnected this wire.
This doesn't surprise me considering some of the other debauchery I've found.
Some people's kids...

causes
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