a/c charging problems again

[Touchdown038]

Well I bought a kit to retrofit my system to R134a (yes I'm aware of the temperature and pressure differences) because the Freeze-12 wasn't working out for me.

So I had my system vacuumed out this morning by the local Napa auto shop, and I took it straight home and began charging with R134a. But, I didn't even get halfway through the first can, and the low side pressure was reading around 65 PSI, which according to the gauge is higher pressure than even a full charge.

Anybody have any ideas why the pressure is so high? Could the vacuum have gone away already, leaked out somewhere? There really shouldn't be 65 PSI when only half a can is inside the system.

[NISTECH]

when you charge the system you need to have the car running and the A/C on.

[Touchdown038]

Yep, had it on with the compressor engaged... I've read countless threads and web pages about this, and I don't think I did anything wrong with the charge. The adapters are all installed correctly and the refrigerant flows out just fine.

So supposedly if I had lost my vacuum, would the excess air in the system cause this high pressure problem?

[NISTECH]

and only introduce the charge on the low side when the car is running. Never under any circumstance do it on the high side with the car running.

[NISTECH]

you could have a refrigerant flow problem. What is the high side when the low is at 65 psi?

[Touchdown038]

I am definitely charging on the low side, on the hose that comes out of the evaporator to the compressor.

As for the pressure, I'm not sure, because the gauge is inline on the charging hose.

So I'll get a hold of a gauge tomorrow and test the pressure. If that side has pressure, I'm thinking air in the lines, due to a leaky vacuum (not likely). If there is low/no pressure on the high side, could it be due to the compressor not pushing refrigerant through the system?

[NISTECH]

restriction in the expansion valve likely. what you will be looking for is low pressure on the high side. somehwere below 150psi. out side temp plays a large part on A/C pressures. the coler it is out side the lower the pressures will be ,the hotter the higher.

[Touchdown038]

True, and with an 89-degree day today.... ugh, gotta get the A/C working.

Brand new expansion valve though, it can't be shot already... is it a problem if I didn't insulate the pressure (I think) sensor on the expansion valve?

[tar0icy_w/tapioca]

well i just retrofit mine too, and i'm on the second day of R134, i had a problem with the compressor not taking in any refri. when i first try to charge it, here's exactly what i did and for some reason it workedafter i retighten the adapters i use a combination wrench (10mm) to push down the valve needle (where the air goes in/out) and found that there are still quiet a bit of pressure in the compressor, i kept the valve open until i absolutely can not hear any more air coming out of te compressorei turned on the car and turn on the AC (it shouldn't work at this point because u have no pressure) but have it on anyway, then make sure ur can of refigerant is upside down, and the meter right side up, i attach the quick connect hose,my compressor slowly draws in the refrigerant, after the compressor turn on the gauge read like 100+ psi but after i shut off the can it read only ~20 ish so i open up the can again until it ran empty, and on the second can i just keep shuting off the valve and checking until the gauge reads 45 psi, and now my AC is working good, though i think there is still some raw air and R12 in my compressor because my compressor was not vacumned properly, on yeah any one know if it is dangerous to have R12 sprayed on ur skin???

[Touchdown038]

Well, the system is charging. Just out of curiosity, I pressed the low-side needle valve until there was no more pressure. Mostly just air came out, almost no refrigerant at all. I then proceeded to hook up the can and hose with the a/c on and 10 minutes and one very cold can later, voila. I had to stop because the car started to run a little hot, halfway to the next mark on the temp gauge (only running rewired stock electric fan for a couple of days) but I don't think that will be a problem when I am driving, just at idle. Low side pressure is sitting at 25 PSI right now, and everything is looking good so far.

Anyways, thanks for your help so far guys, I'll let you know if anything goes wrong down the line.

[NISTECH]

R-12 can freeze your hand but will not do any damage just making contact with it. What you have to worry about with R-12 is if you get enough of it in the air you are breathing it can displace the oxygen and make it very difficult to breath. The other more deadly problem with R-12 is if it gets sucked into the intake of you engine and goes through the combustion chamber it will come out the back as fosgene[sp?] gas. Very deadly can kill you in a matter of seconds if you inhale it.

[s13EastTN]

So you guys jsut let the car run out until it was empty, even tho the pressure said something like 100+ and then it came back down to normal after you took the can off? If so, then that would solve my "don't wany my a/c to blow up if I recharge it" problem.

[Touchdown038]

No, I had about a quarter of a can in the system with 65 PSI of compressed air (or so it seemed by what came out when I pushed the valve. For some reason, letting out the air and R134a mix and then recharging it kept the pressure down.

But it's normal to have high pressure with the compressor not running.

[tar0icy_w/tapioca]

just get a good gauge, and get a reading all different ways (with engine running, not running, cooled, not....) and then see which one make sense, but if ur AC is not leaking, then u will need to find some way to cycle out the old refrigerant, that's where shop comes in, u notice that their machine extract old out and pump new in, if u want to take a risk, get a fan aim it away from u, and let out the old and repump with the new

[tar0icy_w/tapioca]

oh yeah, i did mine in the open with nice breeze coming through so i think the R-12 disperst pretty well....hope no one got caught down wind, if i had know i would of spend $30 dollars to get it pumped out