Just thought I'd share: I charged my AC with R152a, which apparently performs better in an old R12 system than trying to make R134 work. Something about the pressures and temperatures being closer to R12. Also R152a is compatible with R12, R134, and with the oils. It's also cheap. Sounds too good to be true?

After a lot of research I went for it. Here's all of the tools and supplies I used:

Vacuum pump for AC systems (has other uses too):

AC gauge set:

R12 Fitting adapters:

Can tap:

2 cans of R152a:
https://www.walmart.com/ip/648338081


After screwing on the R12 adapters, I hooked up the vacuum pump and gauge set, ran the pump, observed nearly 30 in-hg vacuum on the gauge. I let it run for 5 minutes, closed the valves, turned off the pump, and left it alone for 3 hours. Checked the gauge, still showing same vacuum. At this point I felt it would hold a charge. With gauge valves still closed, disconnected pump and attached the hose to the can clamp. Clamped it onto the can of R152, and opened the low side (blue) valve on the gauge set to begin charging the system. Started engine, ran AC on high recirc. Tilting the can you can see liquid being drawn into the system through the gauge sight glass. You have to tilt the can from time to time to keep it flowing. The can will get cold during the process and when empty it'll return to room temp. Meanwhile I set the can down and stuck a thermometer in the AC vent while waiting for all the R152 to be drawn in. Only took a few minutes, tilting the can frequently and seeing the liquid in the sight glass means making progress.... How much do you need to charge the system? An old timer said a good rule of thumb is "When the vent is blowing cold, it's enough. Don't overcharge." After one can the air was getting cooler. Closed the blue valve when done with the first can. My experience with AC is that something in the 40-50F range coming from the vents from an old system is plenty acceptable. Wasn't quite there yet, so I started the next can. AC vent temps got down to about 49F with the car idling in the garage and getting very little airflow. Success! I finished off the second can, closed valve, removed can. Done! If overcharged, the compressor will labor - this will be very obvious, belt will start to squeal. To confirm I had approached this threshold, I started a third can and could immediately tell that was going to be too much. I believe it was reading 50 psi on the low side when the belt started to chirp, and I recall it was in the mid 40 psi range when I originally achieved the 49F from the ac vent. So, I just cracked the blue valve open a tiny bit to vent off some excess pressure, the belt stopped its occasional chirp, I kept going a little more just to create a margin of comfort, low side pressure was back in the low 40's, and vents were still blowing cold. I'm sure there is some correct high side pressure which could be observed on the other gauge, but I'll leave that for future research.

Too long, didn't read? R152a works. I have 49F blowing from my vents idling in a hot garage (it was 95F outside!). Took it for a drive, AC on, feeling very luxurious. Two day later, went for another drive. High 80's outside. Toro AC still works. This refrigerant is environmentally friendly and dirt cheap, so venting is no problem, and if it needs another charge next season, no problem. Next I'll charge the 86 jaguar. Hopefully I'll be 2-for-2.

 

Hopefully it works for your Jaguar too.

I used Freeze12 (R12a) in my 86 Ford truck and it worked great. Once it all leaked out I tried to recharge the system with R152a and never got it to blow cold, but maybe there's some other fault in the system.

 

A continuation of this...

The AC still works well, but the 95F+ ambient temps and some extended idling has revealed what I believe is an issue. That scenario causes temperatures and pressures to rise in the system (as expected), and typically an AC compressor has some way of dealing with that, by shutting off on pressure or temperature limit, until back within acceptable range. Mine is not doing that for the above scenario. The issue reveals itself with some rhythmic belt chirping, and can be confirmed on the gauge set. Obviously I can turn off the AC myself when this happens, but that's not ideal.

Is this system or compressor itself supposed to have overpressure cut-off so it cycles to handle this situation?

 

I think I found the answer: Possible superheat switch on back of compressor, and thermal limiter gizmo. But my compressor doesn't seem to have the switch on it.

https://classicoldsmobile.com/forums...3/#post1463739