1994 Toyoto Camry..The air conditioning works fine most of the time. I have serviced it and pressures are good with duct temp at 45 degrees. While driving, all of a sudden there is no cool air, almost warm coming out of the vents. It stays like this for a while and then everything is fine again. When it does this the compressor and the cooling fans are working. The evap is not freezing up.
Any ideas......I am thinking it might be the expansion valve getting stuck open. ???

It could be an over or under-pressure condition caused by some blockage in the system or too little/too much refrigerant in the system which shuts the compressor down. Are you sure the compressor is actually running when it occurs? If it occurs all of a sudden and disappears as fast, then I would not expect it to be an expansion valve that is open too much. Does the A/C light stay on when it happens?

dave mc

As far as I can tell the freon is good and the compressor is running and the A/C light is on..... If the system gets "too" cold and the expansion valve goes to open to warm it up and then sticks open, does that sound feasable.

The one time I saw this it turned out to be the expansion valve. There is no better blockage in a line then a stuck valve. We did everything under the sun first but, nothing worked until we had the valve changed. Just a bit of limited experience with this fail mode.

As far as I can tell the freon is good and the compressor is running and the A/C light is on..... If the system gets "too" cold and the expansion valve goes to open to warm it up and then sticks open, does that sound feasable.

Maybe. I don't have enough experience to say that is a reasonable failure mode or not. Did you service it yourself and pull a decent vacuum to evacuate it? It's maybe possible there is moisture freezing near the valve. Does it only happen when the cabin load is low and the vent temps are quite low? If it's feasible, you may want to attach the gauges to the ports and stick those to the windshield so you can check them when it happens again, or at least be able to stop and open the hood immmediately and observe the readings.

dave mc