'90 190E A/C took a dive (found a good thread but can't find it again)

Here's the deal! Last summer the A/C would come on when it was first turned on and only run for a second or so and absolutely would not come back on. I didn't try it again until today. It was flat...so I added gas till it wouldn't take any more then fired everything up...and the compressor ran, and I added gas till the sight glass was almost clear...the suction line was very cold....there was very cold air coming out of the vents...then the suction line started getting warm...suction pressure started going up...but the compressor was still running because the pressure went down some when the RPMs were increased...and then the compressor quit and absolutly would not come back on.

What's going on?

So I waited for things to cool down and tried it and still no compressor. That thread I couldn't find mentioned a switch near the windsheild wiper arm. Has something to do with flap positions. Anyone have a clue?

[psfred]

Replace your serpentine belt, it's slipping and the Klima relay is switching the compressor off.

You also need to find and fix the leak, then evactuate (apply a hard vacuum for an hour or more) the system BEFORE charging, especially with R134a -- water vapor will cause the formation of hydrofluoric acid. The acid will corrode EVERYTHING in the system, including the teflon coating on the compressor pistons!

Peter

You don't suppose that's why I'm getting a code display 11, "A/C compressor engagement signal for idle speed (circuit 87Z) missing".

The belt does even seem loose, I wouldn't be surprised if it was original. Do you think with the belt being loose, that theres a good chance that the tensioner may be faulty also?

What type of device monitors the slippage of the belt?

Thanks alot Peter

[psfred]

There is a Hall effect pickup on the back of the compressor that generates a speed signal for the climate control.

Either the belt is slipping (check condition -- if a lot of the rubber ribbing on the inside is missing, it will slip on the AC compressor) or the compressor clutch is bad or dirty. The tensioner can be bad, too, but that usually wont' result in a belt slipping without a screech or whine. Belt usually goes to the bad place pretty fast, too!

It is possible that the speed sensor is bad, but that is usually only a result of a worn out compressor or a bad rebuild.

Peter