I just recharged my 1986 190E and the problem I had before is still there. Unless I am moving and the RPM's are off idle my AC works. As soon as I stop and the engine idles my Compressor shuts off and of course has to be reset via turning ignition off and back on. All is well then. If I rev in Neutral and hold the gas at anything over idle the compressor will still work. Any ideas!

Either the engine speed sensor, the compressor speed sensor (if this car has one) is faulty or belt is loose/slipping on the compressor pulley. When the Klima relay detects a speed mismatch between engine and compressor rpm, it cuts off the compressor to protect the belt. The difference in speeds should be greater than about 30% to activate the cut-off. In the procedure I listed in this post, there are steps to check the voltage signals from these sensors.

I will look at the troubleshooting guide I have. I went through the steps to troubleshoot in my troubleshooting efforts. It involves pulling your klima relay, jumping two connectors to force the compressor on (for short term only) and taking a reading between two other contacts. The problem is, i cant remeber which contact is which.

The usual cause for this behavior is a slipping belt. Check the side with the grooves -- if there are cracks or pieces missing from the ridges, you need a new belt, and likely the problem will go away.

Sadly, you will also likely need a new belt tensioner too, a royal PITA.

Peter

Belts not slipping at all. Funny thing is it actually worked fine yesterday. When it shuts off the pressure on the low side is about 34psi. Maybe I just need a hair more R134! I know the low pressure switch point is 2 bar so maybe it is too close. If I held the RPM's up near 900 ish when at stop lights the compressor never kicked off and I was surprised when I got in the garage and idle'ing that it was still engaged. Also no matter what CC unit I use, have tried three, the darn normal AC button does nothing. Only max AC works. Being that you guys have done more than I have I am wondering if there is an easy answer or not. I will go through the tests over the weekend when I have more time but for now was wondering.