Keep the POA and expansion valve set up. All driers made now can handle r134a. I personally would keep it R12 also.

When not running, the system is equalized meaning both hi and lo side PSI are the same. The lo side gauge does not indicate the same PSI as the hi side so the lo side pegs. Perfectly normal.

I don't have a way to charge it. Need to take to the shop and they can't get to it until the first week in Aug. Yes you do have a way to charge it. Two hours of running a vacuum is not overkill. That system was open for a long time. If the pump usage doesn't cost you anything, let it run a long tim...

Those venture pumps are a POS. If you're waiting a week or so, pull the best vacuum you can and place the system under positive pressure.

Hot wire the fans to 12volts as a test. As soon as the key is turned, the fans come on.

I have never seen brass caps for R134a either factory or replacement. You can get them for R12 systems thru HVAC supply stores.

Thanks Tim and Cusser, It looks like HNBR O-rings come in black or green. They may not be exactly the same (e.g. different durometer) https://www.globaloring.com/oring-colors/ I guess I'll assume the QD fittings for R134a will be OK. It makes sense after all this time at least the R134a fittings sh...

I had to copy your image into Photoshop to sharpen it enough to see the scales. Let's imagine the needle is at the 30 psi position. The first scale (in light blue) is the R134a scale. The temp of the refrigerant at sea level is 35* F. The next scale (green) is the R22 scale. At the same PSI, the tem...

Best way to verify a refrigerant charge is to recover and weigh the proper charge. As you get experienced, you can fudge it. In today's vehicles, the charge is small so a few oz can make a difference.

System can hold a vacuum and still have a leak. Dye is your friend.