AC Service Ports

The caps that you are showing in the photo come off and that is where the valve stems are.

https://www.classicautoair.com...ves-on-your-cars-ac/

Excellent, thank you JFFR!

Do I also vacuum from those valve stem ports or the ones I showed?

William

Ah, so I connect on the ports I show but manually open and close the valves. Perfect.

So the good news!

1. I was able to open the compressor valves as instructed. I had the charging hoses disconnected and the system was empty.

2. I tested the AC switch; the compressor solenoid sounded and the condenser fan ran nicely.

2. The system held vacuum for a long time. Both needles never budged.

I added 1 small can of R12 and  2 oz of ester oil. Both pressures were around 55 psi.

The bad news:

I started the car and added about 1/2 can of R12 and the high side pressures keep wanting to go above 300 psi. (See video) The evaporator temp never dropped from 80 and the condenser coil never got hot. I guess there’s a blockage?? Expansion valve or dryer??

Please help!!

William

Do you have the valves on the compressor at the mid port setting? if you have the lines blocked off there is nowhere for the compressor discharge to go.

Yup. Closed all the way and then open 4 revolutions to open midway as per the instructions.

William, know there is a so-called 'final filter' in the side arm of most Pantera OEM expansion valves, under the dash between the glove box & console. It is a tiny conical brass screen that catches pieces of dryer can media, flakes of rubber off hoses etc, etc. Mine was plugged solid so practically no flow. Replacement e-valves don't have the screen, apparently to increase flow & thus cooling. To remove, fish it out with a hooked scribe and soak in solvent to clean. It just sits in the valve. But 50 yrs is a loooong time to 'sit' if no one has ever cleaned it.

Oh, and replace the dryer can; I cut an old one apart and what was left in there you wouldn't want to flush down a toilet! Originally 1/3 full of small moisture drying pellets.

Good to hear from you Bosswrench!! It’s been a while, I hope you’re doing well. Thank you for the screen advise, that sounds like it might be the problem. If the dryer is 5 years old but was never used or charged, would it need to be replaced?

Its a guess in that case. The dryer dessicant is basically pellets made of the stuff in those little paper packets in medicines etc. Fluid flow swirls them around inside the can and eventually they break down.

Found my culprit. The screen at the expansion valve is clogged!

So I cleaned the filter and replaced it, and I have cooling for the first time in 15 years!! My discharge temp is 50 deg F., but I have bubbles in my dryer sight glass so I may be undercharged.

Correct, since you are using R12 you are most likely under charged if you are seeing bubbles in the site glass.

BTW, this approach does not carry over to 134A. Bubbles are not a trouble sign for that refrigerant.

Larry