I have a 1994 850 Turbo with 212,000 miles on it. My air is acting up all the time now. When doing driving on the Interstate and pretty much going the same speed, the air works great. As soon as I do some city driving, it stops blowing cool air. I have to turn off the AC for 3-5 minutes and then turn it back on to get cool again. The cooling will only last a few minutes before I need to turn off the compressor for a rest again. I've noticed mist in the air once I turn back on the AC after one of these rests.
I took it to a dealer in NC and they drained the system and recharged it. They put dye in the system and found no leaks. This was right before the Winter months, so I didn't use the AC for many months. Since then, I've moved to Florida and of course need the AC. I brought it into the dealer here and they put dye into the system and told me my evaporator was leaking. The price floored me, so I decided just to pick up the car. The service rep said the service man thought my temperature sensor was defective and that could cause the problem. The service guy smelled a burning smell when the air was turned on, and I have noticed it as well. When I pressed them if the evaporator was bad also, there was a hesitation but they said yes as well. The evaporator is $650, the temperature sensor is $650 and the labor is $650: ($2000 JOB!, Yikes!)

Any thoughts on this? Thanks for your feedback. My email is daveshear@aol.com