Air Conditioner Refigerant Temperature Sensors...

[turbokinetic]

Hey folks. Been a while since I have posted here.

Our 95 Aurora had a very gradual, slow, increase in A/C vent temperature. The compressor, condenser coil, and other parts have less than 15,000 miles on them however they are a couple years old.

In troubleshooting it, I found out that the compressor was cycling off at about 50 PSI low-side pressure. This should be in the range of 25 - 30 PSI. In studying the manual, I found out that the compressor cycling is determined mainly by the temperature of the low-pressure refrigerant line. There is a sensor in this line mounted behind the engine.

While it's easy to get to, the bad part is the sensor goes directly into the refrigerant line. You must discharge the refrigerant before it's possible to change the sensor.

After replacing this sensor, the system now cools like new. It is ice-cold.

Hope this helps someone else find this problem! I usually work on older simpler cars where there's a simple pressure switch that controls the cycling. This is completely different and it threw me for a loop diagnosing it.

Sincerely,
David

[southstar]

Thanks for the info.Do you have a part number and brand of the one you used? I need to go through my AC soon . 30 on the low side sounds cool.

[southstar]

I repaired my AC. Watching the gauges, the compressor cycles off at 30 psi and cycles back on at 45 or so. The service manual states 22 psi. It was about 72 degrees outside. Driving down the road, the vent temperature would cycle from 40 to 44 degrees as the compressor cycled. Low side port is before the evaporator on the Aurora.Other cars I own the low side port is after the evaporator and work best at 29 to 33 psi. They also have a temperature sensor on the evaporator to cycle the compressor. AC works great. I am just wondering if should go lower psi before cycling off ? Or is it normal at 30?

[southstar]

After studying the 1995 service manual some more, the compressor should cycle off at 30 and back on at 46 psi. It was 86 degrees today and I had vent temperature of 37 degrees without much compressor cycling. Evaporator temperature would be 4 or 5 degrees colder than the vent temp,which is just above freezing . Working great .