Chrysler Repair: A/C High Pressure Problems, pressure transducer, model chrysler

Question
Hello, Our 1996 LHS with 3.5 engine A/C stopped working a few weeks ago. (note: prior to that it worked okay, then only worked sometimes. And while the car was running at idle in our driveway, we heard a high pitched "squeal" later recognized as the compressors release valve) We replaced the compressor (used) and the line at compressor gets cold but blows hot air in car, high pressure reading climbs to 435 then blows coolant out release valve in back of compressor ... Our local Chrysler dealers parts dept. suggested we replace the expansion valve ("H" valve, located on the firewall), we did, now line at compressor gets cold, and blows "cool" air in car, high pressure reading climbs to 435 then blows coolant out release valve in back of compressor. Our mechanic is a certified GM mechanic and admits that Chrylser's A/C is different than GM and Ford. Our mechanic says there's some type of blockage on the high pressure side but doesn't know where else to look. Any Ideas!  

Answer
Hello Richard,
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 you might discuss that with the mechanic or parts counter person at Chrysler dealer as a possible reason for the over-pressurization of the system. I assume that it may sense such a situation and cycle on and off the compressor as one of its functions. It looks like a simple D-I-Y task.

If it proves correct or you find another answer please let me know. Best of luck!

Roland