AC problem

I have a 1997 4.0 Aurora. I just had the AC compressor replaced and it blows cold when it works. When I start the car cold the AC works fine. Operating water temperature is around 230 (Arizona). Once the car gets to temperature and I stop (turn off the vehicle) then turn the car back on (before the water temp completely cools) the AC will not blow cold (the fan works but blows hot air). This occurs even if the temperature gauge reads well below the 200 (example 120) range. Is there some type of thermal switch or other switch that I can check to see what is shutting off the compressor? Where would these switches be located. I do not believe that I have an over pressure situation shutting the ac off. Any help would be appreciated thanks

Wes

I have a 1997 4.0 Aurora. I just had the AC compressor replaced and it blows cold when it works. When I start the car cold the AC works fine. Operating water temperature is around 230 (Arizona). Once the car gets to temperature and I stop (turn off the vehicle) then turn the car back on (before the water temp completely cools) the AC will not blow cold (the fan works but blows hot air). This occurs even if the temperature gauge reads well below the 200 (example 120) range. Is there some type of thermal switch or other switch that I can check to see what is shutting off the compressor? Where would these switches be located. I do not believe that I have an over pressure situation shutting the ac off. Any help would be appreciated thanks

Wes
I have a similar problem on my 1999 F150. The AC works fine on startup but then it quits sending cold air after about 20 minutes. I checked the pressure on the low side and on my meter it was in the red danger zone at about 75psi. The compressor does not engage when this happens. I was wondering if there was a compressor high pressure switch or valve that could be the problem.
Kaprice

Thanks for the input. I took my car in this weekend to a good mechanic. At this time they are stumped. They say there is nothing mechanically wrong with the system. They can turn the compressor on permanently by applying a voltage to the clutch. They monitor the signal to the clutch and they can see it turn on and then off. They have replaced the high side and low side switches. They are actually going to bring someone else in this week to take look at it because it is so far out of the norm.

Regards,
Wes

there is also an overtemperature switch/sensor of some type. If the car gets too warm it won't let the A/C system come on. It could be too hot when you go to restart or not be working correctly.