A/C problem
 

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!
Mark