I just recently completed a bunch of work on my 1995 E300D (82k miles):

• Replace upper engine wiring harness with used 2004 harness
• Coolant flush
• Delivery valve seals
• Glow plugs
• Oil change
• Air filter

Now, when I run the car, the AC compressor is always on. Even if I put the car to full heat, I get heat out of the upper and lower vents but I also get air out of the center dash vents. I’ve double checked all the wiring. I did notice that the new harness came with an extra connector that was zip tied and folded up. The Zeichnungsdatum (drawing date) of the harnesses matched the original of 10.05.93 so it’s strange there was an extra connector. This connector was near the back (rearmost) of the harness plastic housing.
I had the battery removed for the entire process. I suppose my CCU could have just decided to take a dump at this coincidental time but figured I would see if anyone has any ideas. Thanks!

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1986 420SEL W/1990 560 SEL Full Power Interior Swap
1995 E300D
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Ac compressor is supposed to cycle on and off in all positions except EC and O.

Temp wheel position should have no effect on that.

So to get this right: is your ac compressor stuck on all the time the engine runs?

Christuna, thanks for the reply. I did not realize it was supposed to be cycle on and off at all times. Thanks for that info. I thought using the EC setting for economy should not turn on the compressor. Well, mine is on even when using EC. I also figured it would not come on with the the heat all the way on. My experience before was with the heat on, I should not get airflow from the dash vents...just the upper defrost and lower footwell vents.

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1986 420SEL W/1990 560 SEL Full Power Interior Swap
1995 E300D
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I am having similar symptoms on my 1992 300TE. @foolio, have you arrived at a resolution? Thanks!