Air Conditioning R12 System Maintenance

[PursuitSpecial]

It's that time of year again and it's super hot driving to work. The Aspen doesn't have AC, which makes it nice and roomy under the hood and the nice floor vents provide a cool breeze with the window cracked, but my Gran Fury doesn't have floor vents and it's obnoxiously hot in the summer. I want to see if the AC will still work but all the R12 appears to have leaked out in the 20 years since grandpa used it last. I need some equipment to test the system to see if it has a bad enough leak to worry about, does anyone know where to get the fittings you need to hook up to an early 80s mopar system? Also I want to avoid retrofitting it to use R134, apparently it has a higher vapor pressure and can damage some components. Has anyone used the "envirosafe" R12 replacement? Also I read about people using propane in their cars after R12 was banned, but that sounds like an explosion hazard.

 

[AMC Diplomat]

Envirosafe is butane/propane. Propane actually makes a great refrigerant.

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You could just run that and save the headache

 

[Ark]

You can get simple high/low port adapters on Amazon for hooking up to gauges and AC service machines with the current 134a style ports.

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Envirosafe is a flammable hydrocarbon, pretty much like propane. IIRC it's also illegal to use in vehicle AC in a number of states. If you're one of those states, a shop definitely isn't going to do it.

At minimum you'll need a manifold gauge set, fittings, and a vacuum pump. I would pull vacuum on the system and watch it for a while to see what your leak situation is. If there's no vacuum drop you can see at all, it might be worth trying to DIY it with the Envirosafe without cracking the system open at all. You'll have to learn how to charge the system yourself, which involves pulling a vacuum on the system, injecting new mineral oil, and using a scale to infer by weight now much refrigerant you've added. This is tricky at home and it's why I'd rather just pay a guy with an AC service machine to charge it.

If you've got enough of a leak to warrant taking things apart, then I'd probably just commit to the 134a conversion. No point opening the system without replacing the dryer, no point opening the system without replacing the o-rings, no point replacing the o-rings and not replacing the valve. You'll need to rent a flush tool to purge the lines and condenser/evaporator (easy), and will need to drain the mineral oil out of the compressor. Very important that no old R12 mineral oil is left. Button everything up and roll it down to the shop for a vac and recharge with R134a and PAG oil, and make sure they do the math on the appropriate fill spec, as it's less than R12. There's another type of oil out there that supposedly keeps traces of R12 mineral oil from causing problems, I haven't personally used it.

It can be tempting to just buy a can of Envirosafe and try to "charge up" the car like a pizza driver in an AutoZone parking lot in July. The problem is the system could have been discharged for 20+ years and you don't know the internal condition of those lines and components. If it's all gunked up from exposure to atmosphere, you won't be able to bring it back to life with a can. At least vac everything out of the system and start from empty.

 

[Mikes5thAve]

There's no pressure issue wirh R134 to damage components and in these cars its a pretty basic system to begin with.
They did used to say it doesn't cool as well after being converted or needs more for the same performance but the biggest issue like ark said is making sure the system is evacuated properly of all the R12 stuff.
The existing fittings are standard R12 unless its been converted already, nothing special is required to hook up guages.
You can always use a screwdriver to quickly press the scraeder valve to see if there's any pressure in the system still but if it doesn't work you have work to do anyway unless you find a cheap source for R12 to add to it or use one of the compatible recharge kits. That's if no one has already messed with it before.

 

[AMC Diplomat]

You can also start hunting estate sales. Lots of dead guys left cans of R12 in their garages. They're out there.

 

[Aspen500]

R134a uses barrier hose, however,,,,,it was found that the years of having mineral oil in the hoses, they effectively turn into barrier hose. Trace amounts of mineral oil don't hurt anything. As mentioned, a 134a charge will be about 85% of R12 charge. The PAG oil amount is the same as the mineral oil capacity.

My '79 Aspen is 134a and it will freeze you out, so it's as good as R12.

As for some refrigerant being flammable, so is the R1234yf in newer vehicles so............

IF you decide to use 134a, keep in mind, the sight glass WILL have bubbles. That doesn't mean it's low on charge like it does with R12.

 

[Ark]

R134a uses barrier hose, however,,,,,it was found that the years of having mineral oil in the hoses, they effectively turn into barrier hose. Trace amounts of mineral oil don't hurt anything. As mentioned, a 134a charge will be about 85% of R12 charge. The PAG oil amount is the same as the mineral oil capacity.

The only reason I'd replace the hoses is because you're 90% of the way there on the labor by the time you've unhooked them to drain the compressor, replace the dryer, replace the o-rings, and purge the components.

But, that's assuming lines are available and cheap, which might not be true anymore. I wouldn't sweat reusing them if I had to, the worst thing that could happen is topping the system off every year or two.

 

[80mirada]

Lines are not available new, nos aftermarket ones show up on eBay, or find a shop that can rehose your line sets.

 

[Mikes5thAve]

Aftermarket ones used to be readily available but show out of stock now with the quick search I did.
Nos can be hit and miss since it is old rubber now.