My 1995 W140 S320 has recently developed a weird probelm that whenever I start the car again after it has rested for a short time, the A/C compressor doesn't engage. In that event, I would shut down and restart the engine and the compressor engages again and works in perfect order until the next engine shut-down. Except for that, the A/C is freezing and I don't see any other things being abnormal. That does not happen at the first start of the day but just occurs when the car has been used. After reading the valued article "Mercedes-Benz A/C Control Diagnostics, Steve Brotherton, ImportCar, June 2000" on this site, I decide to start with the basic - The compressor control relay and the low/high pressure switch. Would anyone please tell me the exact locations of them on the W140 and their part numbers if possible? If there is any other idea about the problem, please suugest. I greatly appreciate any inputs.

I had a problem when accelerating or drivnig thru water it would quit and not come back untill the engine was restarted, check your belt tension. It seems they had a circuit to compare engine and compressor speed, this was later discontinued.

Check to see if yours has a speed sensor on the A/C compessor. Had the same problem on my 1990 300E. The speed sensor will "lock out" the compressor and can be reset by shutting off the ignition and restart.

I have an w140 400EL-93.I have the same PROBLEM. I CHANGED the V belt and Cabine (Evaporator) sensor, but no solution. Looking for the wiring diagram, the only relay is the auxiliary coolant pump control relay, but there is a base module computer. Apparently this base module releaf the relay. This is confusing me, since looks like a different a/c system, even for MB cars. No technicians want to work with this. I have to doit by my self. If I get A SOLUTION FOR SURE i WILL LET YOU KNOW. IF YOU GET IT fIRST ,I AM HERE.

THANKS

WILFREDO

did you get a solution?