Most modern cars before mid 2010s took R-134 Freon.

Mahreeoh17 said:

Most modern cars before mid 2010s took R-134 Freon.

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Thanks! Something like this should work then?

Remember, You also have to pull vacuum to the system and if lines been open a while, I'd add some ac system oil and leak detection dye too

I have used freon with dye and leak stop before in a pinch to get me through, but I don't recommend relying on it. Certainly put freon leaded with dye into the sysyem so you can find the leak though.

@Sirius1995 is right with pulling the system into a vacuum. If the system has been leaking for a while and/or the air isn't blowing cold, then it's likely you have outside air (and moisture) in the system. The receiver/dryerwill take care of some of that, but the moisture in the system can cause all sorts of problems (erosion, crystalizing damage, acidic environment...). Pulling a vacuum not only checks for leaks, a vacuum lowers the boiling temp of water (just like pressure raises it). Once leaks are fixed and the receiver/dryer is replaced, drawing into a vacuum and leaving it there boils off and removes moisture from the system. It's the right way to fix a low freon issue.

CKOPOCT said:

I have used freon with dye and leak stop before in a pinch to get me through, but I don't recommend relying on it. Certainly put freon leaded with dye into the sysyem so you can find the leak though.

@Sirius1995 is right with pulling the system into a vacuum. If the system has been leaking for a while and/or the air isn't blowing cold, then it's likely you have outside air (and moisture) in the system. The receiver/dryerwill take care of some of that, but the moisture in the system can cause all sorts of problems (erosion, crystalizing damage, acidic environment...). Pulling a vacuum not only checks for leaks, a vacuum lowers the boiling temp of water (just like pressure raises it). Once leaks are fixed and the receiver/dryer is replaced, drawing into a vacuum and leaving it there boils off and removes moisture from the system. It's the right way to fix a low freon issue.

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This was really well worded, better than in my old automotive school books

if you buy r134a refrigerant on ebay its can come labeled as envirosafe and flammable. its technically propane.

I have run propane in a r134 system and it cools much faster than r134.

you can also run r12, it cools quicker like propane but is not flammable

you should not run 1234yf in your system as it has a higher operating pressure. you can convert a 1234yf system to run on 134a, the 134a cools better than the 1234yf

you can also run computer air duster in the ac system, but its typically not as cost effective as propane.

but yeah you want to run r134a

What about seal compatibility between r12, r134a, and propane? Not that running propane is a wise choice imo. A propane leak around a hot engine... I like the explosions to happen inside the combustion chamber.

I also thought that the r134a systems were designed to run at a higher pressure than r12, so r12 isn't compatable with r134a.

More info here:

Thanks, Marty. Kinda confirms what I remember about non-compatability between the two refrigerants (particularly the oils).

A good flush of the complete system to get the R12 oil out is good for it. I flushed my 1994 Caprice system, installed new components as needed, pulled a vacuum on it and refilled her. She was ice cold.

CKOPOCT said:

What about seal compatibility between r12, r134a, and propane? Not that running propane is a wise choice imo. A propane leak around a hot engine... I like the explosions to happen inside the combustion chamber.

I also thought that the r134a systems were designed to run at a higher pressure than r12, so r12 isn't compatable with r134a.

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r12 runs at lower pressures like propane. typically best operating range is 40psi low side. the compressor uses the oil, not the refrigerant. in the old days when r12 was more common in cars you could just refill the r12 system with 134a. I never bothered to switch the oil out, and never suffered any consequences from it

1234yf is also flammable.

im not saying you should run propane, but most refrigerators and small appliances already run it for their refrigerant systems. my comment was more based towards caution if you buy r134 online or from ebay

If you add R134 Pag oil to an old R12 system that still has some R12 oil in it, it will turn the liquid into a brown milkshake. Ask me how I know. I can see it in the site glass of my receiver dryer on my old 67 Camaro.
Now I need to flush the complete system and put in a new dryer, as it is full of the crap. Just my experiences if you don't flush your system first.

Thanks for the explanation. My last professional working with a/c systems was back in the 90s at the changeover, so I appreciate any info I can get to add to/remind me of things.