1984 300D Turbo diesel

I recently replaced the ignition, instrument cluster, and pulled out the old stereo (didn't replace it, just threw the non-functioning one out). Now I cannot get any activity from my climate control unit. The buttons don't do anything, and no activity from the blower motor. I happened to have another CCU that I know works, so I popped it in and still nothing. I check the fuse and it's fine.

I can tell you that the sensor that goes from the CCU to the auto-climate thingy on the dash (the little black square in the center of your dash) is unplugged, but I thought that only worked when the CCU was set to "auto" climate control.

I know it's not the CCU itself, which leaves the blower motor and possibly the ignition, right? How can I find out if power is actually making it to the CCU?

Or am I missing something else completely?

I did pull a vacuum on the Climate system, which it held well, so Vac issues are off the table I think....

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1984 300D

Defrost should bypass all sensors and apply full heat and full fan to the windshield.
Many people have been down this road. Mine have always at least worked somewhat, and just needed little things. Let us know what you find.

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83 300SD Dark Silver Dark brown inside