I have a 91 190E 2.6 with a strange problem. When I start the car the ac compressor comes on for about 4 seconds and cuts off. When the compressor does run the tachometer goes nuts. If I start the car and run at very fast idle the compressor does not shut down intill I let it return to idle. I've replaced the compressor with a brand new one with a new speed sensor, I've replace the MAS control unit and the belt is not slipping. The pressures are fine and It gets so cold it hurts when I run it at fast idle. If anyone has any ideas I would greatly appreciate them.
Did you replace the drier unit? One possiblilty is that the high pressure switch on the drier unit is faulty. You can prove this by disconnecting the two wires from the switch and connect them together to see if the compressor remains on at idle. The purpose of this switch is to shut off the compressor if the high pressure side gets too high. My 190E was doing this when the auxillary fan had a blown fuse.
Linear Mode
