My a.c. compressor will not dis-engage. It stays on all the time even when I have the heater on. The top slider control is broken and it is stuck on max a.c. Shouldn't the compressor shut off when I turn the fan control to the off position? Also the display on my radio doesn't work most of the time. Sometimes when I crank the car, it will come on, but most of the time it will not. Any ideas what could cause this? My mechanic bill is getting way too high! All of this is on a 1990 740 GLE with the 16 valve engine.

Mine is an 85 but I think that part is basically the same. The compressor is not controlled by the fan switch, but only by the top control slide switch. It is not that hard to take out the control assembly. You can replace it yourself, perpaps with one from a junkyard. There are four screws holding the control assembly. You have to pop the plastic cover off first by prying under the bottom right corner. There is a plug with two wires for the compressor that is separate from the fan wiring. The only tricky part is that the heater vent control cable is stiff and kind of difficult to remove. The vacuum control connections are removed by poping of a single large plug on the back.

If you want to check that your compressor will in fact turn off, pop off the electrical connector on the pressurestat (attached to the receiver dryer)

As for the radio, it should be wired to the bottom of the fuse box. The two problems are probably not related.

R Duke