PeachParts Mercedes-Benz Forum - View Single Post

Jeremy5848 · #3 07-02-2006, 07:19 PM

Seems to me that there is a sensor that detects whether the compressor is actually turning (instead of being frozen). If the compressor is frozen, the lack of a signal from the sensor tells the ACC not to engage the clutch since this would fry the belt, which also runs something else important (the water pump? I forget). This same sensor is used to run the tach. It thus sounds like there is a problem with this sensor or its wiring or the ACC circuits that handle it.

I'm not sure why it would work in Defrost mode, but that mode does do some things that no other mode does. This is, specifically, put the fan on high speed and go to full-on heat by turning off power to the mono valve, which then opens fully. There is probably a problem in your ACC board that creates this combination of symptoms. It appears that there is an almost infinite combination of problems that the ACC can cause, no two are alike. Everyone who posts here seems to have a slightly different problem. You should probably try resoldering the entire ACC board and all connections to it. If that doesn't work then replace that unit.

Jeremy