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Where is the relay for controlling the compressor, or if there is control module for this.
Problem is that compressor is on for about 2 seconds, then stops. If you stop the engine, the compressor is on again 2 sec. after that not at all.

Diagnose is that compressors speed sensor does not work and it stops the compressor
The system has enough gas.

If found out where the relay is i could try to control compressor directly from there

TL

The 6-cyl cars have this function in the KLIMA relay, located behind the battery. However, I'm not sure if the V8 cars have the same setup. If there is not a KLIMA relay, I suspect the function is handled by the BM (Basic Module) inside the CAN box. Might be that the tach signal from the compressor is bad...? Also make sure the refrigerant pressure switch is good, if the system has a proper charge, the switch should be closed (zero ohms).

Couldnt find any KLIMA relay near where the battery would be at 6 cyl cars. Car is 500E 1992. Is any where wiring diagram what shows where relay or digital outup contact is. Could be that basic module. Did find the resistance value for speed sensor, 530-650 ohms. I would like measure from the basic module so the harness is to be measured at the same time. Wiring diagram needed.

It's in the service manual under Electrical Troubleshooting. Here is a direct link to the PDF file (warning - 74MB download) :

http://www.ps2cho.net/downloads/MB%20CD ... TM/ETM.pdf

See PDF page 269 of 275 (printed page 308). The BM does control the AC compressor.

Yes, there it was, Thanks! Useful pdf in the future..