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Convert BACK to R-12 refrigerant?

I have a 90’ Toyota pick up that needed AC repair a few years back. The shop converted to 134a w/o discussing all the drawbacks. My system quit working last summer and I want to try fixing it myself, but w/ R12. I have some mechanical aptitude and experience working on my truck, but haven’t worked on an AC system before. I plan to get an o-ring kit for my compressor from Toyota and overhaul it myself, and I know that the dryer will need to be replaced. Other than that, I have no idea what else I need to do. If I have a shop flush the sytem before charging it, will that be enough? Is there anything I need to do extra when overhauling the compressor or re-installing the hoses, dryer, etc? Any advice would be great. Thanks!

R12 is not available to unlicensed DIY auto mechanics. You can use “Freeze-12” or other R-12 substitutes, but why bother?? There is more, much more, to rebuilding a compressor than just a few “O”-rings…You buy a NEW compressor.

Have you tried adding a can of R-134a and see what happens??

Why go to all that trouble when it may have only leaked a can, or so, of R134a? Do you just like taking expensive things apart?

I plan to have a shop add the R-12, but I didn’t want to spend the time and money working on the system just to have the shop tell me that they can’t charge it because I didn’t -(add hypothetical here)- to my system.
I have the truck torn apart for other repairs at the moment and wanted to hit the ac while I have access to it. Since it’s not running at the moment, I can’t add R134 to see if it works. I had a shop tell me a while back that they wanted $1,000 to fix my system. I can’t afford that, so I’m trying to do it myself. I successfully installed central air in my home w/ no experience, so I figured this couldn’t be much harder. Thanks.

After having the shop quote $1,000 I didn’t consider the simple fix. In hindsight I should have done that. But the compressor is already out and on my table, so any help would be appreciated. Thanks.

What exactly is the problem? Was the A/C performance bad with the R134 before it broke?

R12 is still available, but is incredibly expensive, and generally only available through A/C shops. Frankly, if you’ve never done any A/C work, I would definitely not try to un-convert your A/C. If for no other reason that it’s going to be REALLY expensive to refill your system and so if you did it wrong and the R12 all leaks out, that’s a very expensive mistake.

The AC never got as cold as it did w/ the R12. That’s a problem in the 105 degree Texas heat. After a summer and a half, it quit getting cold at all. I heard from a friend that the R134a eats away the compressor seals when added to an R12 compressor. I was figuring I’d change the compressor seals and go back with R12.

Based on the feedback I’m getting, I’ll probably just go back with R134a again and get on with my life. Thanks for all the help.

The difference in performance in R12 and R134 is 7%. But we get all kinds of questions from people wanting to make odd conversions,I guess it was time for a AC unconversion.

The only conversion they probably did to switch to 134a was to add an adapter to the fitting where the refrigerant is added to the system. They had no choice in the matter. The conversion was required by law when they worked on the system. However, I doubt switching back to R12 would help. The refrigerant isn’t the issue. There is something else wrong with the system that is in need of repair. Besides, I doubt an A/C technician is allowed by law to switch you back to R12.

If you can’t afford the $1,000 to fix the system, you might finance it. Apply for a credit card at Goodyear, Firestone, or one of their competitors that does A/C work. The APR for the card will be high, but for this, you should be able to get six month zero interest financing. As long as you pay it off on time, you will not pay interest. However, if you don’t pay it off on time, you will be hit with finance charges and accrued interest based on the whole period. So don’t do this if you can’t pay it off on time.

I think you are spinning your wheels. Even if you do what you have proposed, I think you will still need to hire an A/C technician and pay more than the original $1,000 quote to get this system running again. Your decision not to pay the original $1,000 might cost you $1,500. Even the best mechanics farm out their A/C work to a qualified technician.

Thanks for the detailed response! I didn’t know about all the legal stuff. As bad as it sucks, I believe you’re right, I need to get this done by a pro. I take a lot of pride in being able to figure things out on my own, but I’ll have to just swallow my pride (and my wallet) on this one. Thanks for the help.

You don’t need a pro to make the switch, you need to fix what is wrong and leave it alone.

In addition to what everyone else has said, if you do manage to switch back to R12, if you ever decide to switch to R134a again, it will be more difficult (and maybe it wasn’t ever done right in the first place) because the refrigeration oils used in the two systems are incompatible and will wreak havoc if mixed. You need to replace the receiver-dryer, and preferably flush the system when doing these conversions.

It has been my observation that R134 requires more air flow at the condenser. The high side pressure seems to go ballistic when ambient temperature is above 90 and the vehicle is idling. Most R12 conversions and some original R134 systems will push the high side pressure in excess of 350psi. when idling in extreme heat. Installing additional fans has been very effective in keeping the pressures in check and the temperature out the vents below 50* even at outside temperatures in excess of 100* and humidity in excess of 60%. I blame many catastrophic failures of retrofitted systems on the ballistic tendency of R134.