Ok so it's hard for me to say how my CCU should be working because it has never worked. At first it didn't even blow but I fixed that and now I'm on to the next thing. I bought a junkyard CCU unit and replaced my old beat up one. The bolower motor speeds work and the off button works but I can't really tell any difference b/w the other buttons. I know I have major vacuum problems so my question is could the lack of difference b/w the other buttons be because of a lack of vacuum or could it be from a faulty CCU? The air is only blowing out at what seems to be ambient temperature no matter what the wheel is at and it only comes out of defrost and the drivers side upper vent. The air is not cool, nor is it hot, just warm ambient air. I read that if there was a CCU failure the monovalve would be stuck open which would make the air hot right? Thanks for the beta!

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1983 300D TurboDiesel

If the air flow is not changing directions then you likely have vacuum leaks. It could either be the actuator pods or the rail of vac connections behind the CCU, or it could be that there is a big enough leak in another system that the climate control system isn't getting enough vac to operate properly. I would plug off all the other system and run the car and see if you can get the air to flow through the other vents. If that doesn't work. Make sure your vac pump is pulling enough vac. It should be between 20 and 25" of vac. If that checks out you likely have leaks in the climate control system.

As far as heat goes, how's your engine temp? If its running below 80-90C you could need a new thermostat. IF the engine temp isn't running hot enough you won't get heat.

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