Earlier this summer I noticed that my AC wasn't getting cold so I took it to get a recharge and the tech found full pressure already in the system. I had them vacuum out and refill the R134A just to make sure I had the correct weight in there. The system did hold a good vacuum.

The AC then worked fine for a few weeks but then stopped blowing cold again a couple days ago. I immediately looked at the little spyglass under the hood and could see some bubbles (which I think is normal) and I beleive the compressor was cycling. I've checked all the fuses and I even checked my fault codes and everything looks ok.

I was under the hood a few minutes ago again trying to figure out what was happening and now I don't any bubbles and the compressor does not seem to be kicking on. I checked codes again and found none. Can anyone suggest what the problem could be? The interior does blow hot air through the center vents and the front fans do come on.

To be honest I have never had a problem with the A/C on any Mercedes I have owned even though I have heard it from many others. On other vehicles I have owned with similar issues it turned out to be an expansion valve. It would seem that you have intermittent blockage in the system and this could be one cause. Another would be the receiver dryer clogged. Just a thought have you gone to the aircondition.com site ? It appears that they have been really helpful for others in the past. Good Luck.
Alan

__________________
92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

The compressor is controlled by various sensors, like pressure, and on the early cars the speed of the comprssor was matched to the speed of the engine. My 92 drove me nots, it would work I would accelerate or hit a buddle it would stop untill you turned off the ignition and restarted it, slipping belt and then bad tensioner. try diagnostics thru the instrument panel.
http://pages.prodigy.net/jforgione/MB_S500.html

Mine would quit because of the hall effect sensor, something like that. what that dose is make sure the compressor is not locked up or the belt is not slipping.
Mine would slip when the car shifted under full acceleration.
The other fault I had was no condenser fan operation and it would fault on high pressure.
You didnt say if the fans were running or not.
Joe

The ONLY way we can advise you on a/c issues such as yours is to give us: High and low side pressures and ambient temperature at time of measurement.

Good luck,

Thanks for the replies. I will try to measure the low and high side pressures and post them. BTW, the two main fans in the front of the car do cycle on and off.

Jerry