My 1988 740 GLE non-turbo can't seem to disengage the AC compressor from working when I put the fan switch on the "O" but still gets you cool air through the vents if you have the air steering going for any of the three AC options on the AC control panel. But once I put it on the any of the others controls the 4th (from the steering wheel in US models) it stops getting me cold air but I am not sure if the compressor is engaged or not.
In a friend's car he changed the AC control unit inside the car from the Junkyard and it worked correctly for some time but it came back again to not work correctly.
What is exactly wrong is it the AC control unit inside the car? Is there some circuitry in the unit that needs to be fixed or is it some vacuum switches that get busted?
During the winter time and good summer weather, I just disengage the AC but pulling the electric plug close to the accumulator.
Thanks guys.
--Hameed.