A\C can't keep it up
 

I have an "89" 260E. The A/C system has recently had the compressor and dryer replaced. Charge has been double checked and is at specs. When you turn the A/C on, it will remain on so long as you operate the car at 45mph +. If you decelerate and/or stop, the compressor shuts down and remains down for an hour or so. I can keep the system up if I press the "Economy" button when decelerating. Once speed above 45-50 is resumed, I can press the "Auto" to have A/C again. I live just outside Orlando, FL so this is not a good option for me.

I've had the system checked out by some local A/C mech's but they are puzzeled and say they don't know which of the several sensors might be causing the problem.

Any ideas?
Thanks in advance!

Sounds like the compressor speed signal isn't correct or the Klima (or MAS) relay is bad.

You will need to find someone who understands the compressor control system on this car. The compressor control relay (KLIMA, usually) gets inputs from the speed sensor in the compressor, the crank position sensor, the temp switch on the evaporator, the PBCU, and the temp sensor on the engine and decides when to turn the compressor on based on those inputs.

You also need to verify that the compressor clutch is good. Ditto for serpentine belt and tensioner.

Usually, a slipping belt or bad speed sensor signal will cause the AC compressor to run for a minute or less, then shut off until you turn the ignition off and back on, so something else is going on here.

Peter

do a search on "a/c cuts out" there are useful info.
before messing around with the acc, ensure your
belts are good and tight, your belt tensioner is in good
working order. good luck!