1965 R12 to R134a conversion

[andy2175m4]

I have a 65 Thunderbird with the stock AC R12 system, it has been empty for years, now I am going to resurrect it, it has the original big cast Iron compressor, turns fine, so I know it will still work.

everything seems to be in order, but I have only 1 can of R12 left, so the only option is to use 3 cans of R134a and refill the system from scratch that way,

I have all the usual R134a AC service tools, for my newer cars, but don't seem to have any of the old R12 stuff left over.

Is there anything I really need to do to convert to 134a other than use ester oil ? Does the R134a really leak out of the old flare fittings and compressor like some Youtube videos claim ?

Is there some sealant I can put on the flare fittings to seal them more tightly ? any other tricks I need to know about ?

I dont mind refilling the ac once every 2 years or so, so if it leaks out in 2 years I am ok with that,

any other advice or ideas ?

[jtschug]

The important thing to note is that the big 2-piston compressors (Cast iron = Tecumseh, Aluminum = York) is that unlike newer compressors, these keep oil in a crank case which is a separate chamber from the refrigerant. You will need to drain the mineral oil out with a one of the two plugs, one of the top, or one on the bottom. There are instructions in the shop manual to check the proper oil fill level in the crank case. It also won't hurt things to add a few ounces of oil (either PAG or POE) to the refrigerant when you charge it (or squirt it into the condenser).

You should change out the R/D bottle when switching refrigerants. The desiccant is probably saturated, and it may have old oil in it also.

Make sure to fully vacuum out the system before filling with refrigerant.

Do not put any sealant on flare fittings. Look them over for any knicks, burrs, or damage, if they look good, torque to spec and they should seal fine. R134a does leach out through the rubber hose material over time, but if the hoses are in good shape it won't be a problem. The other point refrigerant tends to leak out is around the shaft seal on the compressor. The only way to improve that is with a rebuild or a new compressor.

Good Luck.

[andy2175m4]

hey thanks for the input on the Tecumseh compressor, I am draining it and I have PAG oil for the new installation.

question: I have a new R/D and that goes on last, but can I flush the entire AC system with some harmless solvent to remove the old oil ? Would IPA alcohol work for that ?

question: how many ounces of PAG oil to use for the entire system assuming I remove all the old oil in the rest of the system with the flush and run the vacuum pump for a long time ?

[jtschug]

There are solvents made specifically to flush A/C systems.

I’m just guessing, but I would say 3-5 oz of oil circulating with the refrigerant

[jtschug]

The circulating oil is in addition to the crankcase oil.

[andy2175m4]

OK one more question,

now I see that there are solvents that will flush the evaporator side of the system, but I cannot flush the evaporator except with compressed air, because the expansion valve is still in line, and it is so buried under the dash I just dont think its worth it to tear out the whole dash for that. Pushing flush solvent thru the expansion valve is not an option apparently.

all the plumbing on the condenser side and compressor are fine, and I have a new R/D.

so far all I have done is push shop air thru into the suction line on the evaporator side and all I saw was a bit of oil oozing out from the liquid line, as it should be, no junk, no particles, so far.

any other ideas on how to prepare the evaporator side of the system for the new install ?

[Yoda]

May be worth stocking up on extra 134a. After recently rebuilding the AC in my Jeep Grand Wagoneer, I was discouraged to stumble across this article the other day:
https://arstechnica.com/tech-policy/202 ... ollutants/

Guess 134a will be going the way of R12?

This (5+ yr old) article indicates the replacement for 134a is something called 1234YF:
https://refrigeranthq.com/the-end-of-r-134a/

[Alan H. Tast]

Maybe I'll hold off returning the AC in the Roadster for a while...

[jtschug]

1234yf is much closer to a drop in replacement for R134a. GM changes what refrigerant they use in the same car based on which country it was shipping to. The main difference is Honeywell owns the patent and it costs like $300/lb more than R134a. You can even mix the two refrigerants.

[redstangbob]

Maybe I'll hold off returning the AC in the Roadster for a while...

Everyone has their own ideas, I used an R-12 drop in from Enviro Safe on my car and probably another dozen or so for my old boss's collection. It works great in anything with an expansion valve, no good for POA systems without altering the valves. Our tbirds don't have them so.......JMO Bob C

[Cliff Rankin]

From what I can tell as a line mechanic & in charge of a
Commercial fleet. There is still fights going on about
1234 not being the affordable replacement it was promised
To be , plus there are a lot of vehicles using 134.
Also there’s little unexpected 1234 issues car Makers are working though. While we may follow though with the switch , 134 does not even come close to doing the damage that 12 claimed to do. I think 134 will be around for
A long time because so many cars have it now. By the time it’s gone I think 1234 or something
Else will be more cost effective.
My thoughts
Cliff