AC Not working, Very high low-side pressure

[Matt Brandsema]

The AC on my buddy’s 2007 Jeep Liberty stopped working. He said that before it quit completely, it would randomly stop working and only work again if he turned the air off for a little (This made me think “expansion valve!”)

Anyway, I hooked up my manifold gauges and the low side pressure maxed out the gauge! The high side pressure was roughly 150. The car will not turn the AC compressor on, probably because these pressure are out of wack. He said he has not tried to put any refrigerant in it (I initially thought maybe it could be an overcharged system)

I am thinking that maybe there is a blockage somewhere on the low side. What do you guys think?

Topic

[college man]

The compressor was not running and the low side gauge is buried because it only goes
to 120 psi. you have standing pressure. You could have a lp switch issue.

[Matt Brandsema]

Thanks for the reply. (Sorry for the delayed response) . So my understanding is that the low pressure switch monitors the low side of the AC system and turns OFF the compressor when the pressure is too high. If the problem was just the switch, wouldn’t the compressor still turn on?? I am getting no compressor clutch engagement at all. Voltage at the clutch is zero, which means (assuming the wiring is okay) that the computer isn’t commanding the compressor to turn on, which would mean the switch is doing it’s job. Am I wrong in this????

EDIT:
Standing pressure actually makes me go back to the expansion valve being bad. If it is open all the time, then the compressor is pressurizing the entire system, which would cause the low side to go high until the pressure switch kicks if off. It also fits with the earlier symptoms of the AC randomly not working before it went out completely.

[Timothy Salomon]

So do you have 150 psi without operating the compressor? Is the clutch stuck, and turning the compressor even without the engagement solenoid being energised?
If not, then it’s severely overcharged, no matter who did it.
Low side pressure should be 35 psi, high side around 150 psi.
Engine off, both sides will equalize to around 70 psi.

[Matt Brandsema]

[quote=”Timothy S” post=166739]So do you have 150 psi without operating the compressor? Is the clutch stuck, and turning the compressor even without the engagement solenoid being energised? [/quote]

Yes that is the situation.

And no the clutch is not stuck. I can turn the clutch with my hand independently of the pulley when running.

I think I’ll bleed the low side until it gets to around 70 and see if that works

[Larry Bible]

Be careful posting such a statement on a public forum. Venting refrigerant to the atmosphere is a violation of federal law. Recover enough refrigerant to bring static pressure to about 85PSI, not 70. That is too low.

Hope this helps.

[Author]

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