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same pressure high and low side

mmann02ss on Thu February 05, 2009 12:26 AM User is offline

Year: 1997
Make: Chevrolet
Model: K1500 pickup
Engine Size: 5.7L
Refrigerant Type: R134a
Ambient Temp: 75
Pressure Low: 85
Pressure High: 85
Country of Origin: United States

A little background infor - I replaced a bad compressor in this truck about 3 or 4 years ago. Replaced the compressor, dryer, etc. Pulled a vacuum, recharged and enjoyed cold air again. No problems until now. I don't drive this truck much anymore (once a week maybe). I had it out the other day, turned on the a/c and noticed no cold air. So when I got home I hooked up my guages and got 85psi on both sides. I started the truck and turned on the a/c and the clutch/compressor was cycling 3 to 5 seconds on and then 3 to 5 second off. And the pressures never budged on either side still 85. I double checked the manifold to make sure the valves were closed. I even disconnect one side to get independent readings. Always the same on both sides even with compressor cycling. If it was a bad switch, I should still see the pressures move a little in the few seconds it kicks on correct? So is the compressor completely shot? Or something else?

Dougflas on Thu February 05, 2009 4:34 AM User is offline

Sounds as if you're low on refrigerant. Recover and recharge into a vacuum and recharge.

mmann02ss on Thu February 05, 2009 9:31 AM User is offline

What should the static pressure be at 75 degrees ambient. I can't remember from the last time I worked on it but 85 didn't sound that low to me.

TRB on Thu February 05, 2009 10:31 AM User is offlineView users profile

System calls for 32 ounces of R134a refrigerant. Best method would be to reclaim, evacuate and recharge to the OEM specifications.


When considering your next auto A/C purchase, please consider the site that supports you:

JACK ADAMS on Fri February 06, 2009 10:52 AM User is offline

You will need to find the leak first before service. The top three places for this system to leak are at the compressor (case seal), Manifold Hose Assembly (discharge hose) or the Hi-side service port (Primary Valve).

Find your leak, fix it then evacuate and charge to OE specs of 32oz of refrigerant.

Hope this helps and good luck!

Chick on Fri February 06, 2009 10:16 PM User is offlineView users profile

Check for the common belly leaker on those years. Especially if you replaced it with a delphi unit. Check out the Seltic and Sanden replacement compressor offered by this site. They work great and no more belly leaks... I have one on my own truck, going on three years without a problem.. Hope this helps..

Seltic HT6 replacement compressor

Email: Chick


Freedoms just another word for nothing left to lose

mmann02ss on Mon February 09, 2009 9:38 PM User is offline

Thanks for the advice. I'll check for leaks and let you know. Obviously I have very little A/C experience. The static pressure was confusing me. I have since learned that its possible to have static pressure but still be out of refrigerant. At least thats what I've been told. Learn something new everyday. Thanks again.

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