Chrysler Repair: A/C started blowing hot air, chrysler owner, pressure transducer

Question
I have a 2000 Dodge Neon 4 cylinder engine.  I was driving with the A/C on and it gradually started blowing warm air.  That's all I get is warm air now.  I checked the A/C with the gauges and they indicate that I have enough freon in the car. They told me I might need a new A/C compressor. I would like to know if there is a sensor that the A/C compressor might have that needs to be replaced that might be causing the problem, if so where is it?  That way I can be sure before buying a whole new compressor.  Please help.

Answer
Hi Jose,
I am not an expert on A/C and I don't have a manual for the Neon, but a manual for the '96 Cirrus/Stratus shows there to be a pressure sensor in the system. Another Chrysler owner had an overpressure problem with his A/C, and you might have an underpressure problem, both due to this sensor being faulty. Here is what I wrote to him:
"I am really not an expert in AC systems. But as I read the '96 manual for the Cirrus/Stratus model (which is no doubt similar to the one in your vehicle) I see there is a AC Pressure Transducer that is supposed to monitor the pressure in the system and it controls the fans and the compressor. I am not certain whether a failed transducer would result in the system overpressurizing as you describe but it is worth consideration. It is described as being in the discharge line near the compressor and it can be replaced without discharging the system so it won't be an expensive effort to check that out by replacing it. It has a three wire connector: violet white (5V supply), black/light blue(sensor ground), and dark blue/yellow(sensor voltage signal) and these are attached to pins 61,43,and 42 of the PCM in that model Chrysler vehicle. Use a new o-ring when replacing the transducer. It removes with a 3/4" open end wrench."
So look for a fitting on one of the lines that are connected to the compressor that has an electrical device screwed into it with the wire colors that I listed. It appears to sense the pressure by measuring the motion of a thin wall on that line in response to changing pressure in the line, so it can be removed without releasing the coolant from the system. That is my suggestion on what might be turning off the compressor. (I assume that what you observe is that the compressor clutch releases and so the compressor is not being driven when you are getting only warm air. However, if the clutch is still engaged then it would suggest that the transducer is not causing the failure, but rather the compressor is not working or some other refrigerant handling fitting is bad.)
I'd appreciate you letting me know what you learn and how this problem is solved.
Roland