what to do with a R12 system

[freek]

Hi,
Since 5 years I own a CX gti turbo 2 from 1986 with airconditioning. Until last year it did not work. But after a refill with R12 last year it worked fine. Until 2 weeks ago when the condensor started to leak. I replaced the condensor (with a second hand; new Euro 550,-)and I bought a new dryer. I ask myself now what to do; the system is designed for R12 (compressor Sanden sd508), but R12 is not allowed, not ozon-friendly and in fact very hard to get also in foreign countries. When you ask for advise you get very different stories. I have come to the conclusion that in fact very few people do know what they are talking about. What I know now is that only a refill with R134A is asking for a damaged compressor because the mineral oil in the system does not match the HFK gas. Also replacing the mineral oil by PAG-oil suited for R134A is also very risky: the chloor-residues in the system can destroy the PAG-oil. Some say that you also have to replace the gaskets and O rings when you change to R134A + PAG oil. Via internet I got the adress of a airco specialist who claims that he has a relatively cheap and safe way to change to R134a by adding a dope to the mineral oil. By filling it with R134A to 80% of the normal amount of R12 they claim no less cooling capacity. Does anyone who has knowledge of retrofitting has experience with this dope or any advise what I should do best? By the way: Sanden does not support the use of R134a in the sd508 because of greater wear (higher pressures)(source: sanden.com).

[alan s]

I suppose in many ways you've answered your own question; if the compressor won't handle it, then replace the compressor with one that will. I feel the 508 is really quite marginal on a CX when you consider a BX has a 7 piston variety.
There are gases that will "go over" R12 and this could be your solution, but as to what these are in your country is another matter. In Australia the common one was MP52 which was converted by simply replacing the dryer and and giving the compressor an oil change.
I have done a few conversions to R134a and basically it's a case of dropping the compressor out and draining, refilling with new PAG oil, fitting new filter/dryer, renewing all black (rubber) "O" rings with green (Neoprene) ones, evacuating and recharging.
R134a will destroy the black "O" rings eventually just as oil will destroy certain rubbers, and the 'overcoat' gases are predominantly on a sunset life expectancy, so won't be available forever. I can't suggest what the life expectancy of the 508 compressor would be if used on R134a but I have no doubts that we would have plenty over here running on 134a and I would imagine our systems would get much more work than over your way, so persionally, if 134a is all you can get, I'd be inclined to do a conversion as described above and go with it and see what happens. When a more suitable compressor turns up, swap it over then and that would make a permanent solution.
As regards oil residue, I suggest you follow normal practice which is to do the oil change, run for a short while, purge out the gas, drain and again refill with the PAG oil to flush it as best you can out of the system.
Alan S

[fastandfurryous]

I had exactly this issue with my 405. It had an old R12 system (right on the changeover year 1993-1994!) and it was dead. My local bod (who actually does industrial systems rather than car A/C as a living) recommended R413a, which is a blend of R134a and an isobutane. Aparently he's put it in all manner of old R12 systems.
Having changed my condenser, and reciever/drier unit, he did the vac-out and fill up with 800gm of R413a, and the system works. Very well actually. The only problem (as he warned me may be a problem) has been that the pressures are all different, and ideally I need to fit a R134a HP/LP cut-out switch. I haven't yet (and can't without loosing my gas change) so at the moment, I'm having to run with the LP side bypassed. Not good I know, but I do keep a good eye on the sight glass, and will stop using it if it runs low on gas.
This was about a year ago now, and the system is still working very well indeed. I have since sourced all the parts I need to convert to R134a if I need to in the future (Compressor, HP/LP switch, TX valve, seals etc.) but I get the feeling I won't have to for a fair while.
As another interest point on this. I recently got my hands on a CX, with aircon. It's been converted to R134a with a very similar compressor to that used on BX/Xantia models (I'll go and have a look at the model number at some point) and this has worked well. Old cars with R134a Aircon components are turning up in scrappies all over the place these days, so it is getting easier and easier to source cheap parts for converting older cars from R12 to R134a.
PS. All the seals in the 405 are pink. Neoprene?

[BX-Basis]

Basically, there are 2 possibilities: filling the system with R413a will work without changing anything on the system, but not every AirCo service has R413a. Converting the system to R134a means that you have to replace all O-rings in the system and change the compressor oil. Therefore you have to take the compressor out. Normally the compressors work with R134a without any problems, although SANDEN does not recommend this. Citroën (at least in Germany) says, that the R12 syystems of BX/XM/ZX/AX/CX can be converted to R134a without major changes. As R413a is nothing else than R134a with some additives to make it compatible to the R12 compressor oil, the risk for the compressor is about the same with both refrigerants. Converting to R134a gives the advantage of full compatibility to any AirCo service.

[freek]

Hi,
Well the airco is working again! With r134a and the cooling capacity is certainly not less than with R12. This is achieved in a way that very few people know. I went to a specialist who uses a dope which is added to the mineral oil. The result is that the mineral oil behaves like a PAG oil with r134a. So the lubrication of the compressor is not less than with R12. Furthermore it protects the O-rings, so you do not have to change them. For the best capacity the amount of R134a used is 85% of the normal charge. The dope is called Clip-light Retro stick. The adress is: http://www.cliplight.com/ac.php?pageID=Retro-Stick
Regards,
Freek

[rayc]

In the UK there is a direct replacement for R12 call RS24 it's called a "drop in" gas

[Adstar]

Ahha - Someone else has come across R24! So my research is valid. Is R24 an acceptable drop in replacement for the dreaded R12? And just how widely available is it? I'm having the airgon regassed on Tuesday and want to be able to demand the right thing!

In that respect should I also continue to haemorage money and get the drier replaced as well?! (service, MOT, repairs, Retest, Tax and insurance, Oh without forgetting the aircon service! )

[alan s]

If the car needs converting, it can only be done one way; the correct way.
If it has been converted to R134a, there's no point in demanding an overcoat gas as many of these require a different oil and dryer.
If the guy doing the work has run a dye in it, first thing he has to do is search for the leak not just keep dumping gas charges into it; using dye is a modern common (and dodgy) way of leak detection and is useless unless they go looking for the leak which has to be quite minute to genuinely require dye being put into a system. Personally, if I employed a fridge mechanic who dumped a load of dye into every system he serviced, he'd be back on the dole queue in 2 days. For some reason, too many of these guys seem to think if they put dye into them, the leak will suddenly disqappear. If they were doing their job correctly, they'd be looking for the leak before they started, but this dye trick in my opinion is just a way of getting a second bite at your wallet.
There's a few posts on here dealing with the requirements for conversion to 134a or whatever gas they/you decide to use and these conversions must be followed to the letter or in the process of trying to economise, you could destroy your entire system.



Alan S