Compressor whine, excessive low duct temp

[Tonyfeb14]

[*]I installed a aftermarket AC kit in my 2010 Wrangler. It works but with issues I am troubleshooting with the kit vendor but not getting very far.

The temperature sensor supplied with the kit Santech MT0761 looks like it works in the range of 24-36 degrees F.

I checked out the system and have these specs:

Engine RPM: 2000
Ambient temp: 75F
Humidity: 22%
High Pressure: 190 PSI
Low Pressure: 10 PSI
Air Duct Temp: 39-35F ( but continues to go down below 32F when driving, then get some compressor whine)

I suspect the compressor doesn’t turn off and the temp in the air ducts is getting down below 35F. Once the air temp is around 30F the compressor starts to whine at about 2500-3000RPM. I am guessing the evaporator is freezing up. So long as I manually shut the AC when air duct temp drops below 35F and manually turn it back on when above around 42F the AC works fine and the compressor is pretty normal.

I am thinking of replacing the temperature sensor to 34-43F range but the low low side pressure has me concerned. When I shut the system the pressures start to equalize. High side comes down, low side goes up gradually.

Any ideas what ii going on?

[JohnHere]

It sounds to me like the temperature sensor (transducer) might be malfunctioning because it isn't turning-off the compressor at its low limit of 24°F. Is the sensor itself making good contact with the evaporator fins? Recommend looking at that possibility first.

[Tonyfeb14]

Changed the temperature sensor to one with a different range, 34-43F (rather than the kit supplied 24F low range) and now the compressor cycles and maintains a pretty constant air duct temperature. Luckily with this after market system I could make that modification and replace the sensor.

You can definitely hear the compressor when it comes on with a “whoosh” and cuts out quietly. Not sure if that’s a problem but I will live with it since it is maintaining an air duct temp in the green zone (36-44F) on my air temp thermometer.

[Cusser]

Great !!!

Changed the temperature sensor to one with a different range, 34-43F (rather than the kit supplied 24F low range)

I'm not an AC professional, but 24F did seem too low, condensation would freeze.

The "de-icer" thermostat switch on my '88 Mazda truck is specified to shut off the compressor when its sensor reaches 33.8F (1 C). The service manual does not state at what temperature the switch "closes" but believe that happens when the sensor reaches about 38F.