My A/C starts ok, then after driving for some minutes, as it is irregular, it goes off and just blows warm air..and then sometimes comes back on if I turn the engine off, or might just come back on on its own...and if its raining, when it goes off the defroster doesn't work. My mechanic has replaced the control box in the dash a couple of times, and says it sounds like its the compressor, that the bearings are bad and just keep heating up and stop....though after reading some of the threads here I am not so sure. I have found compressors on Ebay for cheap, but my mechanic claims that the Turbo engine requires a different compressor than the non-turbo engine..any thoughts?

I live in Hong Kong and its hot and humid here.

Mine have the same problem and there are two causes.
1. Your R134a is running low in pressure i.e. leak in some where (likely to be the evaporator inside the dash; expensive job) You could try the A/C sealent on the market and recharge with R134a and oil.
2. Clean the condenser in front of the intercooler.

I had a new evaporator, seems to hold the pressure but when in heavy traffic and when the outside/engine compartment temp. gauge reach 59oC or HI, the A/C would still cut off, could caused by over heating.

Would love to fit an extra cooling fan in front of the condenser but there seems to be not enough space. I am also thinking about water spray from the wiper system.

If your AC is cutting out in hot weather you probably need a new AC clutch or at least remove some of the shims to allow the face of the clutch to close up somewhat. Measure the gap in the clutch. If it is around 0.030"+ it will not engage when things heat up. It will engage when it is cool but when the clutch windings heat up the magnet gets weaker due to higher resistance of the wire. (Winding resistance increases from 3.5 ohms to 5.5 ohms) You can remove the clutch, remove some of the spacers on the shaft, and result in <0.020 gap. You might also bypass the over temp switch on the end of the compressor. I spent some time in HK so I know how important AC is there. If you are in traffic turn the temp control to max cold and the blower on high. If you don't allow the compressor clutch to disengage, it will continue to pump out the cold air.
I am trying to find a source for the clutch. It is a Zexel 506491-6961 664 and is made by Ogura Clutch Co. Ltd. I know of three 850's that I can install them on if I can buy them. Do you know of a source in Hong Kong?
If you do, Email me at TomL77@att.net
Tom
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Tom 69-1800S, 72-1800ES, 96-850T

A word of caution. Please be sure to have a presure gauge and check the pressure. By just adding gas to the system it is possiable to overcharge the system as it cools less well when overchaged and cause a leak or explosion. Gas in the eye will result in an imediate frozen and lost eye. If you don,t have some idea of what you are doing, get detailed instruction or let someone who does do it.

I have a similar problem in a 1996 850 turbo with 78,000 miles. The real problem in my case is overheating. The "brain" in this car is smart enough to turn off the A/C when the cooling system goes too far above the normal operating range. The A/C comes back on when the engine cools off a little.

Watch your temperature gauge and see if it goes above halfway just before the A/C cuts out. Mine cuts off at about 2/3 up the operating range, and that happens when the outside temperature goes above 88 degrees in heavy traffic. It can also happen in normal driving when the outside temperature reaches 96 degrees or more.

Another post on this site says the source of this problem is trash, bugs etc. in the radiator. That seems likely since I have had the water pump and cooling system checked over with no problems found. The system is not losing coolant.

i have the same problem and i had my system evacuated meaning vacuum the old system out, put in dye to determine and locate leaks and lastly infuse fresh R134 freon. gonna cost you $80. mine works perfect now.

I just fixed mine!!!!! Added one can of r134a and the temp is down to 45 degrees at the center vent.

Regarding oil leak, becktg, it's not an easy job for DIY and I would let the garage do it. Probably 2-3 hours of labor plus pennies for new seals. By freeing up the flame trap, you allowed air into the system which helps the oil leak out.
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95 854T, 88 780, 88 245

How often does your compressor cycle now? Is it every 5 seconds? Too bad you cannot tell us what pressures you are running. Is it really 45 degrees at the vent?
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95 854T, 88 780, 88 245

Is the freon level correct? Sounds like it's low to me.