I don't think Scotty has ever addressed converting R12 A/Cs to R134a. I saw he mentioned it the other day in his video on the 80s Lincoln, but I don't recall him directly talking about it before.
I started researching how to do this, since I'm interested in converting the R12 system in my '79 Catalina to be able to run on 134a. My system doesn't work, and obtaining R12 is basically impossible without licenses. How difficult of a task is the conversion? Some things I've read have said that R12 and R134a compressor oils aren't compatible and that the R12 oil needs to be flushed from the system. How do you do that? Having overhauled the air conditioner in my 1999 Ranger last year, I learned my way around a/c systems pretty well, and I think this might be something I could possibly do. I have pretty much all of the equipment I need to service an empty system.
The license to buy R12 is very easy to obtain, I have one, it involves paying a few bucks and taking a simple open-book test. However R12 is expensive and can be a bit difficult to find at this point.
To do the conversion at a minimum you need to flush all old oil out of the system and replace the receiver-drier. (You don't flush the compressor, shake all the old oil out of it.) Replacement oil used in these conversions is Ester oil which can tolerate small amounts of the old mineral oil that will inevitably be left behind. Also install R134a fittings for the high and low side. That is both legally required and is just a much better attachment method for the gauge set.
R134a is lighter by weight so you use less of it. The formula is:
(R12 Charge x 0.9) – 0.25 lbs. = R134a Charge
Or you can use a chart:
That's the minimum that needs to be done in converting.
Additionally, R134a molecule size is smaller and it will tend to leak out of old-style non-barrier refrigerant hoses, though the oil that embeds into the hose material provides some sealing. On a car that old it's best to replace the hoses anyway.
You will lose about 20% cooling capacity in the conversion. Fortunately those old GM barges had strong air conditioning and should take well to conversion. For best performance you would replace the old serpentine condenser with a modern parallel-flow type, and additionally add a pusher fan to keep the AC working well when the car is stationary and idling.
How do you get the license to handle R12 and R134a? I've thought about getting a license for that so I could handle larger refrigerant quantities than the goofy cans, and fix air conditioners as a side thing. I could possibly turn a hobby into a self business. I rather enjoyed the time I spent messing with the Ranger.
On the condenser, where do you find new ones? I checked RockAuto and there's no option at all for condensers for the car.
What do you flush the system with, other than the compressor itself? Thanks for the info!
I got mine over 25 years ago when R12a was first being phased out and possibly things have changed, maybe they require people to take a real course now. I found this with a quick search:
https://www.epa.gov/mvac/section-609-technician-training-and-certification-programs
Realistically I think it's better to convert to R134a. I still have some R12a purchased many years ago but I'd convert before trying to buy more when the time comes.
As far as I know there is no license needed to buy R134a but they'll probably do that at some point due to ManBearPig.
I use an air-powered flushing kit and 4 Seasons flushing compound. (I've read that mineral spirits can be used but I have not tried it with that stuff.) You want the air to be as dry as possible so I use an inline desiccant drier between the air hose and flush tool. (Not as good as a pro drier but gets most of the moisture out.)
Replacing the condenser is strictly optional, most conversions don't bother and work OK but might get marginal when idling on a hot day. You'd have to custom fit a suitable sized condenser if you want to go that route.
https://www.amazon.com/FJC-2710-System-Flush-Kit/dp/B0002JMEQW
FYI, I dug out my R12 certification card and scanned it in (personal info redacted). It was issued September 1, 1995 by MACS (Mobile Air Conditioning Society Worldwide). The "training" referred to consisted of an open-book test utilizing a booklet they provided with the application. I do not recall the exact cost, just that it was not expensive. There's a contact phone number though I have no idea if it's still any good.
I'll browse around and see what I can find. I've not been trained as a technician by somebody, but I don't see why I couldn't pass their test. My Engineering Thermodynamics course probably covered a good bit of what they want you to know (pressure vs temps, what phases the refrigerant is in, heat capacities and such). I agree on the R134a vs R12 recharge, the R-134a will be way more practical for servicing, and slightly less harmful if it leaks out. R12 was the nasty Ozone killer, too bad it cools better than 134a, a friend of mine's dad had a Bonneville the same year, he said that air conditioner got so cold you could probably have refrigerated meat in that car. Haha.
To be honest I take the claims of harm done by these refrigerants with a very large grain of salt and believe that the technology changes have more to do with patents running out than anything else. However, this is not an appropriate place to delve deeply into that. As a practical matter we have to deal with the rules that are imposed. I do expect that R134a is going to get the same treatment as R12a in the near future, so I've been stocking up on it while there are no special taxes or conditions imposed on its sale. (As I did with the old refrigerant when the writing was on the wall.)
As I recall the test for that certificate had more to do with proper handling procedures rather than refrigeration theory. I doubt that I have the test booklet around any more.
Those old GM cars did have really powerful air conditioning so you may not notice the loss of cooling very much when you do the conversion.
Can you use R 22 instead?
Not suitable for auto AC systems, it's a higher pressure refrigerant with different thermal characteristics.
I blew it many years ago.
When I read that R 12 was being banned, K-Mart had a 16 oz. can on sale for 87 cents.]1970's or so ]
I should have cleaned them out.
CURSES!
Right now Wal-Mart has the small cans of R134a for under $5 each, which allowing for inflation is the equivalent of about 50 or 60 cents in the 1970s. There is no permit needed to purchase it. You might want to snag some before it suffers the same fate as R12a.