Any automotive a/c experts here? R-12 questions

[SRath]

I have some older trucks and cars with R-12 a/c systems that mostly work, but they are getting low over the years. The two I am concerned with charging or retrofitting right now are a '73 Camaro and an '81 Chevy pickup.

After surfing the 'net and doing a fair amount of reading on the subject, plus my personal not-so-satisfied results with doing an R-12 to R134a conversion on a previous vehicle, the only thing that is clear to me is that there have been so many mixed results with doing conversions and so many "substitute" refrigerants making all kinds of claims that I am heavily inclined to simply stay with the R-12 the vehicles were designed for. Obtaining the R-12 is not an major issue for me. The cost is higher but, done right, should be more-or-less a one time thing, and is worth it to me to have an effective, reliable system.

The '73 Camaro uses the big, long, heavy style compressor and we would like to switch to the smaller compressor like what the '81 Chevy pickup has. More for engine compartment asthetics and the desire to switch to a serpentine belt system than anything else. The Camaro's a/c still worked last summer, but wasn't all that cold. Still pretty impressive given it's age, though.

The '81 pickup, as mentioned, uses the smaller compressor, and still had some charge in the system when I bought it a few months ago (and has some even now), but not enough to turn on. (Why is that everyone who pops the hood on that truck feels so compelled to depress my low-side shrader valve to "check the charge"? In this case, 'everyone' amounts to two different guys who kinda po'ed me when they did that. I gotta get a new cap for that valve so I can slow such people down enough to stop them... )

So, without digressing into an argument of legal or so-called environmental deadends that I couldn't care less about, I would like to know if there is any purely functional compelling reasons to undertake the task of converting the systems to something else and what exactly is involved and recommended? As I said, I once did an r-134a conversion and had less than stellar results and I'm not much interested in doing that particular one again.

I would also like to know if simply recharging the systems, perhaps with some type of stop-leak in the R-12, would be the best 1st thing to try. The fact that these vehicles have 30 and 38 year old systems that actually work and/or hold some significant charge makes me think they are still good systems I should leave them alone and just recharge them. Any good reasons not to?

 

[MMeier]

As long as you have access to R-12, stay with it . I still have 3 vehicles in my fleet with it... the '93 W250, a '90 Grand Marquis, and my faithful ol' 89 4 Runner ( 350k miles on it and the system hasn't been apart yet ) ! My '70 Chevelle I converted over about 10 years ago, and like you, not really impressed with how it cools. Might change out the dryer and go back to the 12. Been buying up all the r12 I can find on Craigslist so I have it... what is it, 134 is going away by 2014 ?

 

[SRath]

Dupont's patent on R134a must be expiring. It was quite profitable for them back when their R-12 patent expired to 'discover' it did the same thing to the ozone as cow and termite farts. I wonder what evil 134 has been 'discovered' to be responsible for?

 

[rscurtis]

Having an '83 Mercedes and spending time on Peachparts, I'll give you the benefit of my experience. These particular vehicles do not like the 134 because they do not have enough condensing capacity. It also runs at higher pressure, which is harder on the compressor.



Don't even consider "designer" refrigerants, use the real thing. As the "designers" leak, different components of the mix leak first, so what you have left is not what you started with.



Keep the A6 compressor, it's the best GM ever made, and has its own oil pump. The R4 is OK as long as your oil supply is good and you never let the refrigerant level get too low.



Don't even think of using a sealer in any vehicle you want to keep. Once exposed to the atmosphere, the entire system is contaminated and will require all new hoses, compressor, evaporator, etc. It's strictly to get the last summer out of a beater before you send it to China.



R12 is such a good refrigerant IMO that I would consider switching my Ram to it if (when) I ever have to work on the AC system. It is easier on the system with its lower pressures and the oil is not as corrosive as the oil used with 134. I'm with you on the damage to the ozone, it's just another scam to sell different refrigerants as patents expire.

 

[SRath]

Is the big Fridgidaire compressor on the Camaro the "R6" you say we should keep? And never use freon with any stop leak stuff, huh?

From what I've read, these two systems must be pretty tight. After all this time, the low freon could be what has passed molecularly through the hoses, which I have read MUST be changed if a system is converted since the newer refrigerants need specially lined hoses.

I guess the best approach for a DIY would be to simply recharge the R-12 in both vehicles and see if they stay charged.

 

[rscurtis]

The A6 is the one you should keep. Looks like a large starter motor. R12 has less of a propensity to leak through hoses that 134 does. Another hazard of switching to 134 is that the system must be completely purged of mineral oil, otherwise you end up with what is called "black death".



If you have or can borrow a good leak detector, charge the system with 4oz of R22 and nitrogen to about 100 psi, and start looking for leaks. You will find more leaks with pressure than you will trying to hold a vacuum.



The A6 compressor was used on many luxury cars in its day because if was the best available, it was even found in Jags and high-end Mercedes. If you ever take one apart, you'll see why it isn't used any more, it's made very nicely, much more that you would expect from GM.

 

[AClayton]

I agree... ... ... def. keep the A6 compressor! That will outlast the car!... ... . rscurtis covered pretty much everything but if you do decide to convert to 134a, the old ref. oil needs to be completely removed and flushed. I have had good luck using the R11 flush sold in HVAC warehouses. After flushing, I add R-22 to 'attract' any moisture then pressurize with nitrogen to confirm no leaks. Weigh in your charge after pumping down to 200 microns or less... ..... if you can't get down to 200, you still have a leak somewhere.



Alan