AC low pressure not pulling down.

[siasil]

Hi All,
I am a tinkerer with a general understanding of AC repair. I have searched the web before coming here and hope that some of you can help me resolve my friends AC issue. She has a 2004 Trail Blazer and they recently replaced the accumulator due to a hole in the bottom if it. They filled the system without evacuating it of course! So, when she came over this weekend, I put my gauges on the system and hooked up my vacuum pump. Then I waited until it pulled the system down to -30. I shut off the pump and let it sit to see if there was a leak. The gauge pressures stayed there for at least 15-20 minutes before I started recharging the system. Once I did, I added Freon one can at a time and watched the pressures come up on the low and high side. The low side however sat at around 70 and I did not see it getting pulled down like I'm used to seeing. they pressure on the low side stayed between 50-70 and did not come down. The high side rose up to about 225 which seemed reasonable since it was in the 90's. The compressor appeared to be spinning and since I had high side pressure, I'm not suspecting it as an issue. What I don't understand is why the low side was not getting pulled down so that it would cycle off the clutch and let the system recover. Is this a sign of an open orifice tube or something totally different?

I know this unit has a problem with the blend door inside the dash not closing, but I would not expect that to cause the low pressure to stay high without cycling. I wlll be fixing that problem this coming weekend as my friend has gone home for the week.

Thanks in advance,
Nick

[Dougflas]

a 30 minute vacuum does not do squat as far as a vacuum. If you do not have a micron gauge, leave the pump on it for a few hours. Your compressor is a scroll type and probably has a control valve in it. The compressor may be in a de=stroked position due to a stuck control valve.

[siasil]

Thank you for the input. I watched a video on stuck valves and it does look like my symptoms! https://www.youtube.com/watch?v=uPUHOnei3g8

However, It doesn't look like this compressor has a replaceable valve like he references. So, will I need to replace the compressor then? Is there a way to confirm the valve is stuck before I do? https://www.getusedparts.com/80/2004-ch ... compressor

Thanks again!
Nick