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brian0918
Posts: 6
Joined: Tue Sep 06, 2016 7:08 am

Re: Diagnosing expansion valve stuck open vs faulty compressor?

Post by brian0918 »

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Last edited by brian0918 on Tue Mar 10, 2026 7:40 am, edited 1 time in total.
brian0918
Posts: 6
Joined: Tue Sep 06, 2016 7:08 am

Re: Diagnosing expansion valve stuck open vs faulty compressor?

Post by brian0918 »

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Last edited by brian0918 on Tue Mar 10, 2026 7:40 am, edited 1 time in total.
mk378
Posts: 77
Joined: Tue May 24, 2016 5:53 am

Re: Diagnosing expansion valve stuck open vs faulty compressor?

Post by mk378 »

I'm more interested in why the high side drops lower than the static pressure. That should never happen unless you're measuring wrong (couplers not fully engaged, manifold wheels opened instead of closed when measuring pressures), or there's a restriction between the compressor and the high port.
DesertfoxTriple7s
Posts: 1
Joined: Sun Jul 29, 2018 11:36 pm

Re: Diagnosing expansion valve stuck open vs faulty compressor?

Post by DesertfoxTriple7s »

High discharge pressure and really low suction pressure normally indicates a restriction on your discharge/ high pressure side. Your filter drier / desiccant sock probably broke open and clogged your condenser. When the high pressure side is discharging into a restriction obviously the pressure goes up. But on the suction side it eventually runs low on refrigerant, if its restricted enough it’ll go into a vacuum. Sometimes restrictions can be hard to diagnose, it could be the expansion valve not opening enough. But your low side pressure would be higher, and normally theirs freezing up close to the valve.
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JohnHere
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Re: Diagnosing expansion valve stuck open vs faulty compressor?

Post by JohnHere »

I agree with bohica2x0. If the shop evacuated and recharged it to spec and your high side is still very low, like you're seeing now, the compressor is shot.
Member – MACS (Mobile Air Climate Systems Association)

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