Automotive Air Conditioning Information Forum (Archives)

mhfd112 on Fri August 09, 2013 6:12 PM

Year: 2001
Make: Chevy
Model: 2500HD
Engine Size: 8.1
Refrigerant Type: R134a
Ambient Temp: 87
Pressure Low: 40
Pressure High: 275
Country of Origin: United States

Pressures were taken at 1200 rpms and vent temp was cold.

I drove 50 miles from home day before yesterday. On the way home the vent temp started warming up and the volume of air coming out of the vents really decreased. I parked the truck in my shop when I got home and let is sit for a few minutes. When I came back there wasn't much water under the evaporator drain. I started the truck and the air was on and a lot of water started coming out of the drain.

GM Tech on Fri August 09, 2013 6:52 PM

classic freeze-up - run it on recirc- hood up low fan for awhile- does it cycle? does all pipes on low side turn snow white? if freezing- then look into a new cycling switch,

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mhfd112 on Fri August 09, 2013 8:15 PM

I just checked, and it is cycling. fan on low and ac on recirculate.

It has been unusually humid here lately. Would that cause it to freeze up?

mk378 on Fri August 09, 2013 8:37 PM

Like any intermittent problem, you have to check when it actually happens (when it is frozen.) The switch can get stuck. If you find it frozen up and the compressor still running, unplug the switch and it should stop. That would confirm the switch is stuck. If the compressor keeps going even then, it could be the relay getting stuck.