Hello, I am new to Mercedes ownership and have an issue with the cabin temperature that leaves me disappointed with German engineering if the situation is normal. I have a 1984 300D, four door, beautiful car with 92K on it. The cabin temperature does not stay a consistent temp. I set the little dial and the heat comes on and stays on forever until the cabin is boiling hot. The it begins to blow cool air and it eventualy gets so cold that it takes all my will power to stop me from changing the dial to a warmer temp. It keeps blowing cold for a long time (20-30 minutes) and then the heat comes back and it too is on for 20-30 minutes. I have taken to a mechanic. The thermostat has been replaced, he replaced some other parts, not sure if the were heat or AC because the same thing has happened there with AC not coming on or staying on to cool the car. Anybody have suggestions for how to fix this? Thanks, Taylor

I actually have a similar issue - I'll be watching your thread. I've been suspecting the cabin temperature sensor (under the center vent in the dash) - but it sounds like you've already replaced it.

Sorry, don't have an answer for ya - I'm sure someone here will recommend something that will be helpful.

Good luck -
James

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

The push button unit itself (CCU) is known as a normal failure item. Remove it and check for cold solders. Also make sure the foam tube behind the glove box is intact. You'll need to take the box out to see, as I recall.

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83 SD

84 CD