Automotive Air Conditioning Information Forum (Archives)

bob234 on Mon November 01, 2010 1:45 AM

Year: 1991
Make: Chevrolet
Model: S10
Engine Size: 4.3
Refrigerant Type: R12
Ambient Temp: 75
Pressure Low: 22
Pressure High: 130
Country of Origin: United States

When it is 75 or colder outside like it is now in Florida my A/C will blow extremely cold. It blows 35 degrees when the suns out and blows 23 at night(confirmed with a digital thermometer) My low side is 22 and the high side reads 130. When it is above 85 degrees the low side will hang around 30-35. Is it ok to run it this cold because it feels great to me?

Cussboy on Mon November 01, 2010 8:40 AM

No - temperatures that low will cause ice to form on the evaporator from the moisture in the air. Systems are designed to shut off the compressor to prevent that icing.

Did you confirm accuracy of your thermometer?

JACK ADAMS on Mon November 01, 2010 12:35 PM

Most GM systems are set to cycle off around 20-22psi on the low side if it is equipped with a cycling switch like yours on the accumulator. As Cussboy asked, make sure you thermometer is correct..

NickD on Tue November 02, 2010 11:07 AM

Cycling switch is more like 25-27 psi for an R-12 system, Can stick that thermometer is a glass of ice water to check for 32*F. First sign of evaporator freeze up is reduced blower air force.

bob234 on Tue November 02, 2010 10:14 PM

bob234 on Tue November 02, 2010 10:49 PM

It doesn't seem to freeze up on speeds 2, 3, and 4. If I put the fan on 1, then it ices over from the orifice tube all the way to the compressor. Then I have to run it on vent mode for about 10 seconds to get air flow again. I just tested the thermometer and it is accurate. I never use 1 or 2 anyway as these pre 1993 S10s have weak blowers anyway. This truck does have a severe duty orifice tube made for 105+ climates. This was used for better idle temps in the summer. Paid a fortune for it too!

ghiotom on Sun November 07, 2010 7:58 PM

So you have a variable orifice tube, I haven't heard good things about them. How does it compare to what you had before?

NickD on Sat November 13, 2010 8:26 AM

Thought you would either adjust or change your cycling switch to the proper range, one of these days that icing may crack your evaporator.