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21st Century R12 to R134a Conversion - Printable Version

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21st Century R12 to R134a Conversion - Rissy - 06 May 2010

Hey people,

Coming on Summer time, and with the thought of the meet this June, I've decided to get my A/C system refilled in time for the event. (Hopefully expecting some lovely warm and sunny weather over that weekend)

Anyway, i'm aware of the old arguments for and against R134a systems, and aware of the pitfalls and tragedies possible for converting an R12 system to R134a, or the alternative apparent simple drop in replacement RS24 for R12 systems.

Talking to someone who i was wishing to refill LEX, and having some backup experience of talking to people, it seems to be very difficult to find someone capable of, or even stocking RS24. My man, therefore, is suggesting, with his previous working experience on other vehicles doing the same thing, and being successfull, and still working many years later, to do the DeLorean with R134a and instead of the normal "PAG" oil, to use Ester oil, which is apparently compatible with any remaining R12 which "might" be left in the system even after a thorough cleaning and flushing, before refilling again with R134a.

Looking at a few websites, i came across this one, which seems to backing up his argument:

So my question is, what do people here think of this approach, and has anyone got any working experience of doing this with either their own DMC's or any other older vehicle? I'm inclined to trust this guy, but am seeking reassurance i guess. Looking at the website above, i'm believing that the whole argument of R134a eating through your R12 system components due to reaction, isn't entirely true, or has been mostly combated against with new techniques...blah blah blah.

If done properly, and thorough cleaning of the old R12 stuff is done, it sounds as though it might be ok to do....

Let me know people, i've got until June 3rd to make a decision whether to let this guy near LEX with his tools etc, or not. LOL!
(I'm getting the Civic done at the same time, which wont have a problem, hopefully, as it is obviously a newer R134a system from first build.)

Re: 21st Century R12 to R134a Conversion - Dangermouse - 07 May 2010


if you are on DMCTalk, do a search on "R134" and you will get lots of D specific advice from owners in hot areas of the US.

Here's one that has been running for 5 years: ... light=r134

My R-12 system was/is misisng parts when I got it (hoses specifically) so I will probably rebuild it as an R-134 system mainly as it is cheaper to get.

It's a toasty 33C in Atlanta this afternoon, and I am not looking forward to the drive home in traffic in my D. Cry

Re: 21st Century R12 to R134a Conversion - stunned_monkey - 07 May 2010

Many AC places will recommend a "conversion" simply because they don't stock the replacement gas

Lex used to hold an R413 charge for up to a year (RS24 is just one blend of drop-in) and it's always been my view that while these replacements are available, why not stick to them? Although the gas is more expensive, it's still cheaper than a "conversion" which will only ever be a compromise.

Drop-in replacements aren't common in the US so they prefer to convert than spend a fortune on genuine R12, which is still legal there.

Lex needs a leak test eithe rway, but the chances are that you'll need to replace an O-ring or something small. This means the charge will last indefinitely, and you'll still be quids in running a drop-in gas.

Re: 21st Century R12 to R134a Conversion - Rissy - 03 Jun 2010

Finally had LEX looked at for A/C today. Bottom line is that the compressor is knackered. Need a new one. Been quoted £200 - £300 for that. Once this is changed, the rest of the system can be proved, or disproved, since the compressor was leaking majorly. Loud hissing coming straight out!
The guy says its not worth trying to repair since he could only use R134a anyway, so might as well get a purpose made compressor for the new gas.
(out of a matter of interest, he did the Civic today, and its now lovely and breezy inside 8) )

I had two options at the time for LEX.

1. Do my own research to identify an appropriate replacement to the old R12 compressor that is knackered. (getting help from you guys)

2. Strip out the original, and give to the guy to find, through his contacts, a suitable replacement before he would return with a new unit.

If i can get LEX passed her M.O.T next week (last attempt IF parts arrive from Ed in time!) then i might be tempted to get the A/C done, so need to fulfil either option 1 or 2 prompt after M.O.T (Tuesday, hopefully) otherwise, if i'm using the Civic for Wales, then LEX's A/C can wait.

I chose option 1 for starts. So has anyone got a good replacement part number/name/serial...whatever?

Re: 21st Century R12 to R134a Conversion - stunned_monkey - 03 Jun 2010

The whole system is R12 not just the compressor. Drop in R12 gas is available and brand new compressors are available from dmc and they aren't 300 quid!

Re: 21st Century R12 to R134a Conversion - Doive - 07 Jun 2015

Did you ever come to a conclusion on this Rissy? Ours is in for some major surgery, and the bloke says our A/C system is incompatible with his R134a gas, and he'll need to do a full conversion of all seals to suit the new gas. I think our system needs some seals replacing anyway, but I could well imagine doing the whole lot would cost £££s.

Re: 21st Century R12 to R134a Conversion - Chris Williams - 07 Jun 2015

I know I had a long chat with Rissy (Chris) about this last year. When I did mine, and I know not everyone will think it was the right way to do it. I had to replace the condensor (radiator) as this had a hole in it, whilst this was out I drained all the hoses as best I could having removed the dryer and compressor. Having drianed the system as best I could I fitted the new dryer/condensor and re-filled the system with PAG oil, fitted the correct valves and had it charged. It's now into it's second season and still working perfectly well. Now I do know not everyone will think this was a great way to do but it did seem to work.