Automotive Air Conditioning Information Forum (Archives)

GKN on Sun July 07, 2013 5:57 PM

Year: 1997
Make: Pontiac
Model: Firebird
Engine Size: 3.8
Refrigerant Type: R134a
Ambient Temp: 85F
Pressure Low: 90
Pressure High: 95
Country of Origin: United States

I am having problem charging the system. I did pull vacuum for 20min and I tried to charge it, but the system takes very little refrigerant (about 6oz). The pressure for Low and High side is about the same - 95psi. The compressor comes on - but the Low and High pressures stay the same. Do I have bad compressor or bad control valve?
I decided the recharge the system because I had similar condition – Low and High pressure were staying at 100psi.

GM Tech on Sun July 07, 2013 8:05 PM

As long as you are sure you have the gage set valves closed (at least the high side) when charging- then you have a bad control valve- if both valves are open- you have an external bypass going on through the gage set......

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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......

GKN on Sun July 07, 2013 10:07 PM

Thank you!! Ordering control valve right away after I figure out the color coding