AC Charging question 89 4 liter weird service valve related

[1989 comanche mj]

I just got a new to me 89 4 liter comanche, had the 134 low side fitting on the compressor.  Had a burst hose.  I was not familiar with these valves on the back of the compressor.  They are exactly like valves on home HVAC.

 

I replaced the hose and put some uv oil in it.  I turned the low side valve all the way in and hooked it up to vaccuum, and ran it for an hour.  It held a full vaccuum, so I went to dump refrigerant in there.  It didn't take much, I started it up and it immediately ran into a vaccuum.  After messing around a bit I realized that the valve needs to be turned in midway to charge and have refrigerant flow.

 

My question is, did I successfully vaccuum down the system, or just pull a vaccuum on the low side internals of the compressor?

 

Basically, could the vaccuum have been pulled through the low side of the compressor over to the high side and through the rest of the system?

 

I have charged lots of cars with messed up high side valves, and did all the service through the low side, however I am thinking that the vaccuum did not go through the compressor, and that I have air and possibly moisture in there and need to start over with the valve mid way.

 

Also, what size is the high side, 3/8?  I would like to get a 134 fitting for it also.

 

I was able to get about 30 degrees below ambient out the vents, not great but probably undercharged somewhat, and is an unknown system to me.  Wanted to let it sit a few days to see if it had any leaks, or see if another hose bursts before I go fine tuning the charge.

[Marine1Texas]

the old fitting is for the r12 system the was from factory 1989. there are two ways of upgrading the r12 to 134a service ports, putting ports over the old r12 or the new hoses with 134a ports built in to them.

 

When ever I vacuum down a system that was r12 going to 134a or unknown info on it, I will empty the whole system, vacuum both sides down. If your system is working as it should the low side can bleed off and still keep a good amount of Freon.

 

If anyone thinks a system has any moister in the system you must change your receiver/drier then vacuum down the system. The reason for the receiver/drier is to collect dirt and moister. once a system has to much moister, you are not far from a a/c system ready to lockup or leak off. moister with Freon will make acid, that will eat thru your hoses , rubber valves and cause internal compressor problems.

 

When every I change a hose I always change the receiver/drier, it is a small cost to ensure the other parts of the system.