Following up on my AC problems. I thought I had a leaky schrader valve but it turns out that the…

barry96

Following up on my AC problems. I thought I had a leaky schrader valve but it turns out that the high pressure side has a GM ball valve that is notoriously bad. So I have to replace that. But when I took the cap off the high side and it leaked, it seemed like it was just 'air'. It wasn't the greenish stuff that came out of the low side. How is that possible?

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barry96
barry96

After finally getting the high pressure valve replaced, replacing the orifice tube and buying a vacuum pump, I finally set out to tackle recharging the system. This pump could only pull 22lbs of vacuum (unless the guage was wrong), I ran it for 2 hours and it held steady when I turned the pump off. I then began recharging. I noticed that the high pressure was not registering anything. Looks like I didn't have that connector open enough (people warned not to have it push down all the way or it might break the valve again!). But as I understand it, the with the compressor off, the vacuum on the low side will work on the whole system - correct?

Anyways, after about 12 oz of 134a, the system was working properly and as I kept filling the compressor did not pull down the low side enough to shut it off. So I emptied a little 134a and it was again cycling nicely (roughly 10 seconds on, 3 seconds off) and the temperature at the vent was 42F.

So the system is working but on only 12oz on 134a. How is this possible or what am I doing/measuring incorrectly?

barry96
barry96

After finally getting the high pressure valve replaced, replacing the orifice tube and buying a vacuum pump, I finally set out to tackle recharging the system. This pump could only pull 22lbs of vacuum (unless the guage was wrong), I ran it for 2 hours and it held steady when I turned the pump off. I then began recharging. I noticed that the high pressure was not registering anything. Looks like I didn't have that connector open enough (people warned not to have it push down all the way or it might break the valve again!). But as I understand it, the with the compressor off, the vacuum on the low side will work on the whole system - correct?

Anyways, after about 12 oz of 134a, the system was working properly and as I kept filling the compressor did not pull down the low side enough to shut it off. So I emptied a little 134a and it was again cycling nicely (roughly 10 seconds on, 3 seconds off) and the temperature at the vent was 42F.

So the system is working but on only 12oz on 134a. How is this possible or what am I doing/measuring incorrectly?

barry96
barry96

Thanks. Seems like this valve does separate (Part #: MT0105) on a 1996 Corvette. I will end up trying that tomorrow if Autozone has the part. Still seems strange that only vapors leak. It's been an ordeal having never worked on AC system before. I hope the air powered vacuum I bought works.

ScottyKilmer
ScottyKilmer

by gas I mean 134a vapors. Often the liquid green oil will not leak out of those valves. And yes, replace the hose assembly as those GM valves are not replaceable separately

barry96
barry96

Sort of lost now. How could it only leak gas? Where is the 134a? Did you mean to replace the hose assembly with a schrader valve type connector?

ScottyKilmer
ScottyKilmer

those just leak, replace the hose assembly. The valve will often only leak gas and not the oil liquid