2001 Tahoe high presure on low side of A/C

idatahoe · Monday at 10:49 PM

Hi everyone,

I have a 2001 Tahoe with the 5.3. The A/C works just barely. I assumed it had a small leak and needed a charge, so I hooked up my pressure gauge + R134A.

Unfortunately, it looks like it cycles from low (below 25PSI or so) to 60PSI on the low side. So the compressor runs, low presssure rises, and the compressor kicks off.

It seems like the high side is bleeding off into the low side? I'm not sure if this indicates a bad compressor or something else.

Thank you!

Tonimus · Tuesday at 9:40 AM

It does sound like it's low. The high pressure cutoff doesn't kick in until some ridiculous pressure.

ORVietVet · Tuesday at 2:15 PM

It does sound low on refrigerant. What is the ambient temp when doing this?

idatahoe · Tuesday at 2:20 PM

Thank you for your replies!

How could it be low on refrigerant with the low side getting up to 60 PSI, then the compressor clutch disengaging?

Ambient was around 60 or 70F when I tested.

Whenever I've charged a system before, it's seemed like the low side goes down when the compressor is running, if it's low. It usually doesn't build pressure, but maybe I'm missing something.

The refrigerant bottle even says to charge the low side if it's low, and if the pressure gets that high then something else is needed.

CPB · Thursday at 4:55 PM

The pressure expected is dependent on ambient temperature, so check an r134a chart. It the clutch disengages and the compressor no longer spins, then pressure should rise.
Some fake numbers as example. The high side will be around 175psi when low is 40psi. When the system is off it'll be at a static pressure. Meaning the low side can be higher when "off" than when in operation.

idatahoe · 2026-06-05T10:44:25-0400

CPB said:
The pressure expected is dependent on ambient temperature, so check an r134a chart. It the clutch disengages and the compressor no longer spins, then pressure should rise.
Some fake numbers as example. The high side will be around 175psi when low is 40psi. When the system is off it'll be at a static pressure. Meaning the low side can be higher when "off" than when in operation.

I understand, but the low side gets up to 60 PSI when the compressor is running, shuts off, and drops to 25 PSI when it's off, at which point the compressor kicks back on. So it's doing the opposite of what you said, it rises when the clutch is engaged, and drops when the clutch is disengaged.