Kevin in Atlanta

I need to print that out!

alabbasi

Depending on the time of year, you can get R12 for as little as $20 / can locally which now seems to be going rate of R134 from Orielly's or Autozone.

Given the level of effort required to convert properly (not just a vac and charge), it's cheap.

A proper conversion requires a flush, maybe a condenser change to a more efficient parallel flow condenser, barrier hoses, oil, drier etc.

If your R12 system is relatively leak free, then a charge would cost you $20 for a one can top up, or $100 for a complete charge. This is vs the thousands that you would spend to properly convert to R134, which will probably not work as well.

There was a time when this stuff was really expensive but now demand has dropped off because the vast majority of cars that required R12 have either been scrapped or converted, and many people have discovered that propane works as a drop in and costs about $3 to charge a system.

The EPA certification is a very simple open book test, anyone should be able to get it. But if you decide not to, I believe that you can still buy R12 for 'resale' purposes.

I suggest that you look on locally and not on ebay. Don't be afraid to haggle as, in many cases, people list it for a silly price only to see it sit on the shelf.

Lastly, bargains are had by opportunistic buyers and not people who suddenly find themselves needing something right away. If you own a couple of cars that need R12, I suggest that you take your time looking, and wait for a deal to come up on a case of R12 to stick on the shelf for future use. This is the worst time to buy , but in December, this stuff is pretty cheap.

76FJ55. Thanks for posting the graph and providing the explanation, you are correct in that the increase in high side pressure is dependent on temperature. But for those of us who don't have control of the weather, we can use less R134 in an R12 system to prevent seals from blowing.

jleidel

Those of us doing conversions are usually doing so due to the lack of cooling due to leaks or other anomalies. In which case, replacing the seals, drier, rebuilt hoses and expansion valves are in order regardless of whether you're doing r12 or r134a. You don't need to change the condenser. At this point, the only difference in parts cost for me is the PAGG oil for the compressor. This cost me ~$8 for a bottle yesterday. The r134a at o'reilly's yesterday was ~$10-$12/can.

At this point, the significantly lower cost of r134a [and the ability to readily find it in the foreseeable future] makes the $8 for PAGG oil a wash.

outbackgeorgia

I have a Griffiths kit and it has worked great using both R12 and now 134a after replacing ALL "O" Rings during the 134 conversion.
Dave

alabbasi

Really? I checked a couple of days ago and the cheapest I could find was at $19.99. I checked again on their website to make sure and the cheapest listed there is also $19.99:

http://www.oreillyauto.com/site/c/se...keyword=r-134a

They may be having a special at your store but In any case, the price if the refrigerant is pretty much negligible when compared to the level of effort required to do a proper conversion. Instead, I went the R12 route and spent my money buying diagnostic equipment to help locate the leak and offending part or o-ring so that I can make sure that the system is leak free.

I'm glad to hear that R134a works well in 928's. I come from the Mercedes Benz world and many models from the same era (like my 84 500SL and 80 450SLC 5.0) have marginal performance with R134a.

Lastly for the sake of forward planing, it may good for members to know that R12 is readily available. It's still being produced in other countries, there is plenty of virgin stock here in the US and plenty of recovered stock.

FYI, R134a is being replaced by R1234yf in Europe. Soon we may be seeing the same issue with R134a that we saw with R12. If this happens, the price will go up.

If I was to speculate, I can imagine R134a costing more then R12 at some point for the simple reason that there are a lot more cars on the road today that require it and demand drives price. It's already gone up considerably in the last few years. I remember buying it for $6/can not too long ago and was shocked to see it costing $20/can. So much so that I bought a jug of the stuff.

Good luck with your conversion.

dprantl

A can of R134a is $10 and readily available. Big Lots has it cheaper. And if you buy a 30lb tank at Sam's Club for ~$85, you will be paying under $2.50/12oz. I'm sure you can find a store selling R134a for $50 a can, but that is not justification for bridging the price gap between it and R12.

Many R134a converted cars have marginal A/C performance... and how many of those are you 100% sure have had a proper conversion?

Like many others, you are simply missing the point. The reason people look to buy refrigerant is because they have a leak in their ~20 year old system. If you go and just "replace the offending part or o-ring" and then recharge with expensive and difficult-to-acquire R12, how long do you think it will take for another ~20 year old o-ring to fail? And then you have to do it again. If you want to make sure you have a reliable system, you need to change all the o-rings in the system. At that point, what is the extra effort to switch to R134a? $50 for flushing apparatus, $10 for mineral spirits, $10 for a bottle of ester oil and an extra 30 minutes of time. Oh, and a new expansion valve, <$50 which is a good idea to replace anyway since it will also be ~20 years old.

R1234yf has serious problems and its deployment has yet again been delayed, possibly indefinitely. There is no doubt that R134a will eventually be replaced by something else, but that may still be years away. If at some point R134a is replaced and it becomes expensive, and the replacement's performance is good, then it will be prudent to convert to it just as it is to convert to R134a at present.

Dan
'91 928GT S/C 475hp/460lb.ft

alabbasi

Really? maybe it's just a different point of view to yours? I can get a can of R12 for $20 all day and all night. But that was too expensive given the number of cars that i own which use it, so I bought a couple of sealed jugs for $300 each, which is $10/lbs.

So per charge, the price difference is not going to be more $50 between the two gases and you'll be using the stuff that's designed for your car.

Two minor notes:

1) Even tight systems will lose charge over the years. One of my cars sat for 10 years and was low freon (but still had a charge). All I did was charge the system and it's worked perfectly, without need for top up since 2008. You'd be surprised how well seals hold up if you stick with R12.

2) Your proper conversion leaves out barrier hoses which are required if your converting to R134a because R134a molecules are small enough to leak through R12 hoses. As many of the cans that you see for sale have a leak sealer (which is really bad stuff). It can create it's own set of problem.

In conclusion, if you want to rebuild your a/c system, you have the skills and tools to do so, then this is great and I champion your approach.

The work that you're describing will cost thousands if you farm it out to a mechanic and many people will as they don't have the tools or the skills. If all the mechanic is going to do is fix the offending leak and charge with R134a (in order to save the customer money), then the system will more then likely have marginal performance and the likeliness of more leaks. For what? the cost of $20/can of R12 vs $10/can of R134a?

dr bob

The common availability of R-12 at $20/can is a myth, at least around here. And while I'm sure there's only one tiny leak in everone elses' cars, mine was not so lucky when I bought it with 22k on the meter. It had leaked all its life, based on the stack of warranty and other dealer receipts for "check for leaks, none found, recharge" that came with the car. I went after the problem with an electronic sniffer, and quickly figured out that there was more than one or two places it was leaking. So I spent the time learning on the job about every connection and part in the system. Rebuilt the hoses, flushed the condenser and evaporator, flushed and refilled the compressor, new drier, new expansion valves, all new o-ring seals at the connection points. At that time I had (and still have) the choice of R-12 or R-134a, and I chose R-134a just because it seemed prudent at the time with the dwindling availabilty of R-12.

The R-134a performance is excellent in my car, with under 20º center vent temps at 85º+ ambients here in relatively dry SoCal. Since the system was bouncing on and off the freeze switch using R-134a, there was and is no reason to go back to R-12 for better system performance. In the 15+ years since I did all that work, I've added a total of three cans of R-134a to make up for leakage while the car sat idle for extended periods. It's a shaft seal leak, and that seal needs to be maintained wet with oil by running the system once in a while.

Had I not gone through the effort of resealing the system, it's likely it could have continued on with it's habit of needing a couple pounds of R-12 every three or four months. I had plenty of R-12 so that was always an option, but it seemed prudent to fix the problem rather than continue to Band-Aid the symptom. I still have at least one 30# cylinder of virgin R-12, plus most of another, should the need to change back suddenly pop up. I've since sold the other several cylinders and the cases of cans that I'd picked up prior to the ban, and before I'd bought this 928.


For those facing the challenge of keeping their 928 cool inside, consider carefully what Dan says above. It's a point that we and others have stressed for years, and that's to fix the leaks in the system, then decide what refrigerant to install. Just adding refrigerant every year, even if you can load up at $20 for each 12oz can, still doesn't replace lost oil. It means that you are still guessing about how much refrigerant is actually in the system. Even if you do get that amount exactly correct when you top up the charge, a little will still leak out every day. So you get diminishing performance from a system that's in a death-spiral from loss of lubrication.

But/if you can find R-12 for $20/12oz can, it only hurts $50 in Freon today.

dprantl

I should also add that the A/C hoses for the S4+ cars are pretty stout in comparison to other makes and I have not had any leaks with them and R134a, at least not yet.

Dan
'91 928GT S/C 475hp/460lb.ft

alabbasi

Bob

I don't think anyone is suggesting that it's OK to maintain a leaky system as that is irresponsible. Leaks certainly should be sealed but there is a difference going through your entire system vs fixing a leak, or creating new ones by just dropping in R134a. If you're not using barrier hoses, then the system will leak. No ifs no buts.

85 degrees? At 85 degrees, I'd have the windows rolled down

In Texas we get up to 110 degrees f on a regular bases in the summer and this is when R134a is completely ineffective on many of the cars that I converted in the past. But up to about 90 degrees, they still blow cool.

davek9

Great info here thanks for posting.
What is the best non-destructive do it yourself leak detection, a dye?

Thanks,

Dave

alabbasi

A UV dye will help detect a leak under the hood quite easily. You can also buy sniffers (cheap on ebay) that have probes that you can use to chase lines and stuff down the vents. They'll make a sound if they detect a leak.

davek9

Does a system need to be fully charged to find a leak, both of mine will hold vaccum >24hrs, but don't hold charge after running AC for more than a day.
I'm thinking compressors, but at ~400 bucks I'm trying to be sure that's where the leakes are.

Thanks,

Dave

dprantl

I am using the stock hoses on my '91 and they haven't leaked in 5 years with R134a in the system. On my other cars, the stock hoses all leaked when converting, so like I said, the ones on the later 928's must be made of better materials.

Dan
'91 928GT S/C 475hp/460lb.ft

alabbasi

David

Are you saying that the gauges don't move at all for 24 hours and then leak? That's odd. Some leaks do appear under pressure which don't appear under vacuum. In that situation, the system would leak down to a certain psi (say 80 on the high side) and then stop leaking.

If you're leaking down in 24 hours, then I would think that you have quite a big leak which should be easily detectible with a sniffer or dye. I prefer using a sniffer to poke around but dye is cheap and usually comes in a can or R134a.

You'll need a black light and those yellow glasses to find the dye. Check the A/C ports and the hose connections, then condenser first. If you can't find any leaks there. Then it may be the evaporator which will require a sniffer to confirm.

Dan,

If your hoses don't leak then they are either barrier hoses from the factory (which could be the case as 1991 was pretty close to when R12 was banned completely in 1993), or that oil had saturated the hoses and may have acted as a seal. That's a long shot, but it can happen, although I wouldn't hold my breath.