It all started several months ago as the temp control wheel was not doing its thing. Driving along and you command a warmer temp with a/c on, I would move the wheel slightly warmer and the blower speed would increase and get colder.
Lately I jump on the car and the a/c doesn't work just warm humid air coming out. At first I could stop the car and restart and the a/c would work (compressor speed sensor?) now a/c will not come on at all. Compressor will not engage.

Please help...all suggestions appreciated

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Wayne Jockers
1992 300D

You are dealing with one of the most obnoxious intermittants known to MBs. Your statement about jumping on it and loosing AC gives a good starting point.

There is a full trottle switch on the throttle linkage that tells the Klima relay to disconnect the compressor at full throttle for more power. It should come right back on when the throttle is released. I would try disconnecting the switch (it should not be left disconnected as it has other functions besides AC cut-out). The car will operate fine for test purposes (I did a big service on a 190D2.5T last week and the switch was disconnected - we didn't do it and the car has been coming to us for a few years now).

The fact that cut-out was initriated and then not released might be the switch but it probably indicates a problem with the Klima relay or it may just be a coincidence or it might be that you get belt flop (speed sensor cut-out) under hard accel.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician