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Low Side High, High Side Low - How can that be?
Posted: Mon May 29, 2017 1:35 pm
by Esox99
Forgive me, I'm a newbie at A/C stuff, but I want to learn how to do what I can since I seem to be constantly plagued by automotive A/C issues. I have a 2000 Chevy Silverado 5.3L truck and the A/C is not working. It was working okay last summer and I did charge it some in the Fall, which seemed to get it going good again. This spring, it is blowing warm air and when I put a manifold gauge set on it, the low side cycles from "normal" (20 PSI) to "extreme" (85 PSI) with the compressor clutch cycling. The high side gauge reads low at 100 PSI when the low side is up and only about 125 PSI when the low side is down.
I can't seem to find a chart that says what this means, but I suspect there is a clog somewhere or maybe the orifice tube is stuck open? Any help would be greatly appreciated.
Thanks,
Esox99
Re: Low Side High, High Side Low - How can that be?
Posted: Mon May 29, 2017 5:06 pm
by Dougflas
you're probably low on refrigerant. Recover and recharge to spec. Doors and windows open, rpm 1500.
Re: Low Side High, High Side Low - How can that be?
Posted: Mon May 29, 2017 6:53 pm
by Esox99
I should have mentioned that I already tried adding additional R134a, but it won't even take any more. It seems to be maxed out and not much more can be added, as if it had reached some sort of equilibrium. I don't think it is overcharged because the high side is still so low.
Re: Low Side High, High Side Low - How can that be?
Posted: Tue May 30, 2017 2:24 am
by Dougflas
you can not determine if the high side is high or not until the compressor runs all the time.
Re: Low Side High, High Side Low - How can that be?
Posted: Tue May 30, 2017 4:22 pm
by Esox99
So, any recommendations on what I should do next?
I suspect that since these are 'abnormal' gauge readings that my compressor is failing or some other control valve has gone haywire.
Re: Low Side High, High Side Low - How can that be?
Posted: Tue May 30, 2017 6:28 pm
by bohica2xo
You have a LEAK.
Topping up a leaky system eventually leads to compressor failure.
There are no control valves in your system. Just a fixed orifice tube.
Find the Leak
Fix the Leak
Flush the system.
Add the proper oil charge.
Evacuate & charge by weight.
It really is that simple.
Re: Low Side High, High Side Low - How can that be?
Posted: Tue May 30, 2017 7:38 pm
by Esox99
I will look for the leak and go forward from there. It will be a learning processes, but that's why I'm doing this. I want to learn this stuff. Thank you!
I do have a couple questions...
Topping up a leaky system eventually leads to compressor failure.
1. Is this just do to the compressor needing to cycle more frequently? Does a compressor normally fail altogether or can it just get 'weak' due to the leaky system?
2. When you have a leak like I do, why won't the system take any additional R134a charge? I started with a fresh 12oz can and it would not take much at all. I could leave the can on there for an hour and it would not suck any more out of the can. I would think that with a leak that I could at least charge more into it and get some cold air blowing temporarily.