Charging Vintage Air System - Sanden Compressor

[ModernMuseum]

I'm trying to re-charge my 69 firebird / ls3 air conditioner that has a sanden compressor with a Vintage Air IV setup. Amazingly, it still had a little pressure in it after sitting for 5 years.

Since I don't have a vacuum system, my ultimate goal is to cycle a little R134a through it since I have a few extra cans and try to relieve any air entrained in the system, if any - I believe I just used a air compressor style vacuum venturi thing last time to try and evacuate it before I charged it, which probably isn't the best vacuum one can achieve.

Anyway, I was draining a little from the system last night and then started trying to recharge it a little from the low side with the vehicle turned off and it didn't appear to want to take any into the system. I tried turning everything on again and the system obviously didn't have enough pressure for the compressor clutch to engage. How long should it take to get an initial charge in the compressor with the car turned off? Listening to the can, the fluid doesn't appear to be moving.

[dontlifttoshift]

With a full 30 pound bottle, good vacuum pulled on the system, and fully warmed up with the heater I could get a full charge in. Outside of that perfect scenario getting a pound in without running it was hard to do. Now I have a machine and that is way better.

With the system off, even low on charge, you could have 75 psi on the low side. How much pressure is in the can? I don't know either.

I strongly recommend having the system evacuated, pulling a solid vacuum on the system for at least 30 minutes and recharging properly. Anything else is just guessing as you have no idea what is still in and you really do not know how much you are adding.

[dhutton]

Autozone and others will lend you a vacuum pump and gauges.

Putting the R134A can in warm water helps.

Don

[ModernMuseum]

Gotcha, I didn't realize I could get a vacuum pump from auto zone. I've never used one before, but that won't stop me. Thanks for the advice guys. When I did have it running a few years back, I wasn't extremely impressed with the system, but then again I do have a completely black car and had some warm air coming in from around the kick panel vents, which I hope I have fixed. Every little bit helps; hopefully I won't have to run it on full gas turbine mode in the summer if I do things properly.

Should I add any PAG oil to the system (I already have some) or not? I guess it should still have plenty since there haven't been any leaks during that time.

[Bobsky]

I would take it to an AC shop and have them vent it, draw a vacuum and charge it to VA specs. If you have pressure in the system, no air has entered. The only way to know if the correct charge of r134 is in the system is to start with it being empty and dry (vacuum ensures that).