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.