Air Conditioning problem
1997 GMC Yukon V8 Four Wheel Drive Automatic 180kkm miles
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I have a 97 Yukon. A/C worked great for years. I noticed the condenser was dripping oil, and sure enough it had vented (seems to have rusted out at the lowest point in the system). So, I replaced the condenser with a new one... doing the job on a low humidity day, the system was only open for about 5 minutes. The old one was still holding pressure too, just not as much.

Then I took it to my trusted mechanic for a recharge. They said it was being difficult and thought perhaps my compressor was bad, but after further attempts that got it charged with "good numbers". However, I noticed it wasn't very cold and the compressor never stops running! Granted the cold side gets cold and the hot side gets hot... if you're running on the highway, you can get reasonable cool air (but not cold). Idling in traffic though... it just gets warm and moist smile.gif

So, like many of you, I hate not understanding... so I bought a gauge set! Just hooked it up and here are my results:

Engine @ idle, fan low, A/C max:

Low 60psi, high 120psi


Engine @ 2000rpm, fan low, A/C max:

Low 40psi, high 150psi


Fan set to max, same results as above.


Ambient temp 74 *f

low port temp ~60 *f

Air vent temp ~58 *f

compressor never cycles, runs 100% duty cycle.


I'm wondering if this might be over-charged? Or is it possible the expansion valve is "open" too much?

Does it make sense that increasing RPM lowers the suction side pressure? (I think it does)

I assume the low side pressure should be lower then it is?

One other thing to note... when the compressor is shut off (a/c off), the pressures balance to about 70psi... which I just read on this forum is about correct for the air temp?

Any thoughts would be fantastic, thank you!

dave

Sure sounds like an overcharge, at idle you wouldnt mind the 25-30 low side at 74 degrees the high side readings will be less than 200.