I pulled out the cabin temperature sensor for the acc. I'm going to try to relocate it so I can put some gauges on the dash and use the hole for wires, etc.
Have a look, does it look like part of its broken off? The climate control works fine most of the time, although it seems finicky sometimes, like its not hot even right next to the "click" for hottest, and then other times its really hot almost all the way to the blue area, maybe it just has some lag time in the adjustment. Anyway, here it is:

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

Yes, the top broke off. There should be some more circuit board and a sensor/thingy at the top. As it is, it won't work. It is supposed to be glued into the black grille and shouldn't be out anyway.
A new one is $30 as I recall, I had to get a special order from this site for it. Fastlane has it unavailable (or you can always get it from a parted out car).

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1984 300DT turbo 138k mi

Still hauling me to school and back.

Handy Site:
http://www.dieselgiant.com/

It was snapped into a little fitting, nothing glued. Looks like a hose from the intake side of the blower sucked air past this sensor. It all seems to go back together okay. I'll have to look around for another one. Thanks for the help.
-Geoff

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

Mine was like that too (http://s151.photobucket.com/albums/s138/arew264/Benz%20Climate%20Control%20Thermocouple/) . I managed to find the other half by some luck, but it snapped about the same way.
It is supposed to be glued into the grille piece, but I'm guessing that with age on ours the glue disintegrated/died/whatever.
Yes, that hose pulls air past it. It commonly disintegrates as well, so make sure all is well there.

__________________
1984 300DT turbo 138k mi

Still hauling me to school and back.

Handy Site:
http://www.dieselgiant.com/