So, I have 1991 Pickup 4wd with a 22re engine, 187XXX miles, daily driver and camping mule. In all the years I have owned it, the AC has never worked and I have never bothered trying to make it. Now, just rebuilt the engine and just kind of feel like I want all the things to work. So, because it's a 91, the AC is R12. Now, I can have a mechanic assess it for leaks and get a repair kit, but since it's R12, I was thinking that I should just replace the AC to a complete R134 system, not simply replace the ports. I see replacement kits from UAC (never heard of em) on Rock Auto and Parts Geek ~$230-300-ish. Just filling my system with the UV freon would cost $160. The kits seem to include pump, condenser, plugs and some other pieces, I don't think they include the hoses.

Has anyone here upgraded the AC system in their old-ass Yota from R12 to R134? Did it do that thing where the project just kept costing more and more money? Was it fairly straight-forward? Does the AC actually work? Did the AC eventually stop working, and did you find out why? Did it feel worth it?

Anyway, any experience or ideas are appreciated. After this, I'm fixing up a power steering system I pulled out of a salvage yard and installing that on my power-steering-free 91. Also very exciting because I have never in my life owned a vehicle with power steering.

 

Mine did not work but was intact and had no pressure. I bought 3 cans R12 and a filler hose to put it in off ebay. It’s been working great for two summers now. Is your system intact?

 

Intact as in all the pieces are there....

 

Here's everything I know about A/C: https://www.yotatech.com/forums/f116...-r134a-284801/
Converting to R134a is just a matter of replacing the o-rings (yeah, the ports too, but those are just conversion fittings). But that assumes everything else works, which in your case, is a long shot. You could start by trying to pull a vacuum on the system; if it holds a vacuum, you could try charging it just to see if the compressor worked. You'd have to evacuate and re-charge it after replacing the o-rings.

In my case, I knew the compressor had failed (the magic goo was leaking out), so I didn't have to worry about testing it. And mine worked until the compressor failed, so I knew I wasn't dealing with a big hole in the evaporator or some-such. If you want to make the leap to a compressor, you could first try getting compressed air into the system to check for leaks. Real A/C guys will say that's a no-no because it potentially introduces water, but you're going to have to pull a vacuum for a long while no matter what.

 

So- the compressor and condenser are the same between R12 and R134a systems, and simply have different o rings? Or just that my o rings are likely trashed because they're 30 years old... Either way, might be easiest and cheapest to replace the whole system. I imagine everything has holes.

 

R134a requires a different Lubricant (PAG v. mineral oil). SFAIK, PAG doesn't play well with old-style rubber o-rings. How bad? Would it leak? Probably.

For a conversion, you can use the same compressor (though it is difficult to completely flush out the old oil). On a newly-designed system, I think one specifies a slightly larger compressor, and probably a few other changes, because R134a doesn't have exactly the same physical properties as R12. But you don't care about that.

To buy R12 requires a special license. I'm sure you could find someone to sell you some under the counter, but I have to say that all the stuff I've seen on eBay labeled with the word "R12" has been anything but the real deal. Often, these are mixtures of propane and butane. Sold as "environmentally safe" (true!), but absolutely illegal because a tiny leak will fill the cab with an explosive mixture.

 

Nice...

 

Mine was intact, but not working when I got my 1987 4Runner. A few years ago I pulled each component and pipe and cleaned with rubbing alcohol, then installed with new o-rings and receiver/dryer. It went faster than i thought. (The evap box was 60% filled with decomposed leaves)
Charged up with two cans of R-134 and has worked fine since. I used R-134 to test, with the intent of putting R12 in if all was ok. But I decided to just leave it and see what the compressor did. so far, all ok.

 

That sounds like the ideal situation. I think I'll try rehabbing this one. Did you try the UV dye/freon?

 

No UV dye. I had borrowed a vacuum pump and a set of service gauges from a friend, so after i had done all the repair work I ran the pump and pulled vacuum, then unhooked. I then let it sit overnight with the gauges still connected. The next day the pressure stayed the same so I figured I was good to go.

I got a o-ring kit that was supposed to be compatible with R12 and R134. I used a O-ring lubricating oil when reassembling.
I drained the oil out of the compressor, then refilled with new. Every other component had been flushed of compressor oil during the o-ring work.
(Running rubbing alcohol in the lines, then blowing clear with compressed air, was the protocol Toyota had us do when doing warranty a/c work whenever a compressor went bad.)
When I had the evaporator out I cleaned the box well, and poured serval pots of boiling water on the fins of the evap itself to kill off any bacteria that may have been present. there was so much debris in the evap box I pulled the heater fan motor to make sure it wasn't restricted with stuff, but it was fine. it's easy to pull, though, especially when evap box is already out. May be worth a look.
Once I got it up and running, and i knew the compressor was going to make it, I ordered the bearing for the magnetic clutch. I got through the dealer(Koyo bearing) and it was surprisingly cheap(around $20.00 iirc). It made a noticeable change on how the engine sounded at idle.