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Repaired and charged but not sure?

58weiss on Wed May 18, 2011 5:00 PM User is offline

Year: 1995
Make: GMC
Model: Sierra
Engine Size: 5.0
Refrigerant Type: 134a
Ambient Temp: 79
Pressure Low: 12
Pressure High: 175
Country of Origin: United States

I recently replaced the following parts compressor, evaporator, accumulator, high pressure switch, orifice tube. Pumped down, charged with oil and replaced 3 lbs of 134a now my question at idle 12/175, off idle at 2000rpms 11/210 and the compressor cycles, ambient temp 79 degrees, vent temp 45 degs. any ideas if why the compressor cycles and are my pressures ok?

GM Tech on Wed May 18, 2011 7:29 PM User is offline

Whoa Nelly!
That low pressure is way too low-- you will freeze up your evap pronto-- What did you do with/about the cycling switch on the a/d? System should cycle at about 21 psi low pressure, not 12.....

There is a slight possibility your suction gauge is off about 10 psi---what are you using for a gauge set?

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......

Edited: Wed May 18, 2011 at 8:10 PM by GM Tech

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