DIY: R-12 to R-134a Conversion (How To)

Roger UK

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Jun 20, 2010
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Yes that thread was an interesting read Rollus . . and reminded me of the issues regarding R134a

I had my Supra's Aircon re-gassed about 10 years ago . . . Lots of garages SAID they could re-gas with R134a . . . others said the system would need converting, due to the higher pressures R134a needs . . . and this was going to be expensive! Other said I would also need all the valves changing (where you attach the gas)

Eventually I found a really helpful guy who said that my system would NEVER work so well on R134a as R12, even after having everything converted.

BUT he had R12 that he kept for classic cars like old Porches, Rolls Royces etc . . . so did a pressure test and R12 re-gas for just £40. He also had the correct connectors for our cars, so nothing needed changing.

He also commented about the quality of the Condenser used in our Supras - he said most other manufacturers' units corrode and leak long before this . . . mine still looks good.

The problem is I have since changed my engine, so need a re-gas . . . and I doubt very much if he still has any R12 (as others have said, it is now illegal to use it, certainly here in England)

So I am also wondering what this HC12 is like, is it the best option for our R12 systems?

I also remember reading that RS24 or R413a would be much better for our systems than R134a . . . is that true? And are they still available?

EDIT: Also just found this post on Ebay about so-called R12 compatible gasses:

http://www.ebay.co.uk/gds/Freeze-12-Refrigerant-R134a-/10000000005615895/g.html
 
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CyFi6

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I wouldn't use anything other than R134a or R12. If you use a parallel flow condenser, converting to R134a is a decent option. Leaving it R12 is the best way to go though.
 

jetjock

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Jul 11, 2005
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^ This. Monsewer, stick with R12 if at all possible. Second, the guy in that thread pretty much knows what's he's talking about except you don't have to go that far when doing 134a. It's best if you do but you don't have to.

On the other hand you can't go too far the other way. At minimum you'll need HNBR O rings (no need to do the compressor), flush the system, and use PAG oil. Don't just drop in the 134 and under no circumstances use an azeotropic like Freeze 12 as a drop in. It'll work but you'll pay dearly for it later. And avoid the cheap conversion kits found in auto stores

Duracool (R12a) is a hydrocarbon refrigerant. Flammable. Not legal in the US for that reason. Dunno about France but if you really want to burn your car to the ground you might as well use much cheaper propane. :icon_razz
 

JDMMA70

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The avg temperatures in the summer in the UK are nowhere near what they are in Texas. i doubt youll see that much of a difference if any with R134a, assuming the conversion is done correctly.
 

Roger UK

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i doubt youll see that much of a difference if any with R134a, assuming the conversion is done correctly.

Yes but it's the cost of the conversion I'm trying to avoid !

That's why I'd rather find something that is compatible with an R12 system.
 

JDMMA70

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It doesn't cost THAT much, just a few components all of which you can change yourself, some oil, flush kit, valves, and seals. All for under $90 usd
 
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Roger UK

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Having seen the guy with all the correct gear just do a pressure test and re-gas last time, doing a Conversion is not really something I'd be happy doing myself . . . and quite expensive to have done by a garage.

That's why I'd rather try and find out if there's a gas which is properly compatible with an R12 system . . . and get someone to re-gas it.

(the problem is that I've come to realise that, having phoned them, most of the garages who offer aircon servicing don't have a clue about older systems and the various different gases available)
 

JDMMA70

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Roger UK;2052707 said:
Having seen the guy with all the correct gear just do a pressure test and re-gas last time, doing a Conversion is not really something I'd be happy doing myself . . . and quite expensive to have done by a garage.

That's why I'd rather try and find out if there's a gas which is properly compatible with an R12 system . . . and get someone to re-gas it.

(the problem is that I've come to realise that, having phoned them, most of the garages who offer aircon servicing don't have a clue about older systems and the various different gases available)

If youre having to get a recharge, chances are your system is leaking anyways. I can see it losing a charge over a long period of time (20+ years) or from just sitting. Changing the components isn't rocket science, its easier than doing the head gasket. You can leave the recharging to a shop, but everything else you can do on your own.
 

Rollus

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Thanks for all the contributions ;)

I'm with Roger UK here, I rebuilt my engine and the gaz was pumped and the system is empty (well, actually fill with atmospheric air and moisture).
I don't know where I can find R12.

Whatever, I'm going to do the mod in this thread (well, not going so far as JJ said, doing the O-rings, and because I have to instal it anyway, the dryer and/or the condenser if they are worn).
Then, and then comes the gaz choice...
a- Should I just go to a shop and fill R134A?
b- Should I service the system myself and put HC12a or Duracool 12a? (I think there is no legal issue in Europe).
 

Roger UK

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If youre having to get a recharge, chances are your system is leaking anyways

No, as I said I lost all the gas due to an engine change. (the previous re-gas was just because it had never been re-gassed from new)

I remind those new to MVAC it requires tools and skills not possessed by the typical backyard mechanic

That's what I figure . . . and why I'd rather stick with a gas that doesn't need any conversion work

Freeze 12 is a combo of R134 and R142b so basically if you put it in an r12 system that uses mineral oil the oil will not flow with the R134 and your system will likely disintegrate

Yes I had also forgotten about the Oil issue . . .

So is there actually ANY gas available that is genuinely compatible with an unmodified R12 system?
 
Oct 11, 2005
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RS24 is just another blend that would not be recommended. The problem is the gases leak at different rates and you end up after a few years with gas ratios that don't properly carry the oil throughout the systems and the compressor fails. With butane and isopentane this one can also become flammable.

HFC 134a
HFC 125
butane
isopentane
 

jetjock

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atmperformance;2052722 said:
Are you suggesting it's illegal because it's a hydrocarbon or because it's Flammable?

Well, both. It's illegal because it's flammable and it's flammable because it's a hydrocarbon. Or maybe I didn't follow.

f00g00;2052717 said:
Freeze 12...It is a combo of R134 and R142b so basically if you put it in an r12 system that uses mineral oil the oil will not flow with the R134 and your system will likely disintegrate.

The 142 is what carries the mineral oil. It's how F12 gets away with being a drop in. The problem is exactly what 3p stated. When that 142 leaks out (and it will before the 134) the oil stops circulating. The compressor then fails and sends derbies throughout the system. Not cheap or easy to fix.

Point is rather than use 80% 134a (what F12 is) why not simply use 100% and put in the proper oil with it? That way the risk is negated.
 

Roger UK

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Point is rather than use 80% 134a (what F12 is) why not simply use 100% and put in the proper oil with it?

But lots of people say that R134a doesn't work well in R12 systems . . . apart from the mineral oil issue, it's at too low a pressure . . . plus you need all the connectors and O-rings changing, many say you need new hoses too.

Just spoke an aircon guy here in England and he says RS24 is a good R12 drop-in replacement - it works well without any modifications (but he's at the other end of the country to me)

I'm really confused about all these conflicting comments on different websites !!

EDIT - just found ANOTHER suggested drop-in replacement for R12 . . . R409A . . . this doesn't use any R134a - any comments?
 

JDMMA70

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I dont know what to tell you, you've seemed to come to a conclusion that youre happy with. The consensus here is to either stay R12 or Convert to R134a. Again with you living in the UK, you will probably never reach ambient temperatures where the difference between the two refrigerants will be evident. As long as the conversion itself is done properly, mind you replacing the parts required is stupid simple. You can leave the charging to a local shop.
 
Was trying to find a new condenser but here in Finland no one can provide it for supra. Is there any other toyota model that would fit?

The link in first page goes to PartsTrain page but can't find a fitting one there either.

Was planning to use R12a but will go r134a. It's the most commonly used refrigerant here so it's the cheapest option for me. Going to change all parts and then go to a a/c shop. Flush, leak test and refrigerant fill is about 70...80€ so it would be much more expensive to get the R12a (+ equipment) since I have to order it abroad.

Everything else is ordered except the condenser.

Great write up JDMMA70 :thumbup:
 

Emeraldage

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Oct 13, 2011
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Just checking on this again, I'm abotu to redo my system. I'm going 2jz which has a r134a compressor. Is it possible to still use r12?

Another important question, where can I still get the paralell flow condensor? I've gotten a few part numbers looking stuff up, one being 1039293 from american condensor. Is this right?
 

Nick M

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jetjock;2052694 said:
^ This.

On the other hand you can't go too far the other way. At minimum you'll need HNBR O rings (no need to do the compressor), flush the system, and use PAG oil.

^ This.

Let me add you can get generic O-ring kits for R-134 at the autoparts stores that sell the R-134 in a can with a nozzle. If your system is empty and not under pressure, change the O-Rings. If you know somebody with a vacuum pump from Harbor Freight, pull to vacuum for 30 minutes after you change the O-Rings.