AC doesn't get cold

[AirmanPika]

So I was taking a look at the A/C. I connected a pressure tester which was showing me about 38psi at ~83F (may have been in the upper 70s in the garage actually). Car was off so the compressor was not running. When the car is running the compressor clutch seems to kick on and off just fine as do the cooling fans. I've read around and this seems to be normal unless I misunderstood. The AC doesn't get cold at all but the pressure seems to hint the system is still where it should be. Any thoughts?

[WHO1DMC]

So I was taking a look at the A/C. I connected a pressure tester which was showing me about 38psi at ~83F (may have been in the upper 70s in the garage actually). Car was off so the compressor was not running. When the car is running the compressor clutch seems to kick on and off just fine as do the cooling fans. I've read around and this seems to be normal unless I misunderstood. The AC doesn't get cold at all but the pressure seems to hint the system is still where it should be. Any thoughts?

For a sart.
1st the compressor has to be running to show correct pressure.
2nd I would check the hot water valve to the heater it could have failed or the vacuum line.
I had a vacuum line failure myself this year.
That's if you're A/C was working recently.
Now for more help you should start a new thread for your problem.


Dave B.

[Ron]

If the system is at ambient temperature (engine not ran for hours), checking the pressure with the engine off can tell you if the charge is extremely low. This seems to be the case here because, whether 1 can or full, at 80F it should read 87.2psi for R12 (90.2psi for 134a), when the charge has been allowed to match the ambient temp. You shouldn't see 38psi unless the charge was 41F for R12, (43F for 134a), or while the compressor is engaged (which you report it was not).
The compressor kicking in and out every few seconds would be another sign of a low charge.

If you suspect the water valve, flap operation, etc., check to see if the accumulator is getting cold.

You really need a gauge on both sides and to record the pressures shown when the compressor kicks OFF.

[AirmanPika]

Ron...thanks for breaking this off.

That said and as recommended...turned on the system and it is dead as a doornail. 5psi. She's empty.

I looked at the related systems as Dave recommended and they all check out so I know where my issue is now. She held up several years so I'm happy where the car stood. I'll address from here.

[AirmanPika]

It is fixed. Just needed more coolant. I also determined that the leak was actually from the low side valve. The cap also wasn't completely sealing it off possibly due to age. I installed an R134 conversion valve over top of it and that has sealed it back off. Better solution than replacing the whole compressor (at least for now).

[Ron]

In case you didn't know, the valve can be changed and there is a tool that allows changing it w/o losing the charge.

P.S.

[David T]

The caps are only to keep the valve cores clean, not seal a leaky valve. To seal a leaky valve get brass caps. You *could* try to tighten the valve core and see if that stops the leak but generally if a core is leaking it should be replaced. Do NOT try to use an ordinary tire valve, they aren't made for the temperatures or pressures of an A/C system. If you convert and add an adapter you should remove the valve cores and use the valve in the adapter. Converting to another refrigerant doesn't fix the leak that caused the refrigerant to escape unless it was JUST the valve core (it's never only one leak).

[AirmanPika]

All granted and true. For now tho...I'll stick with what I have as it works fine and if it becomes an issue again I'll consider the valve replacement. Besides with the added adapter I can use some more modern tools to measure pressure as needed.

[ttwo]

you could be a sticky if so!!

[David T]

Actually it is already done. Get out your Workshop Manual and go to N:07:01. Also look up ST-29-11/81