mmurphy77

My A/C system is original. I have to 'top off' the R-12 about every 3.5 years which I think is pretty good for a 42 year old system. I've read about these HC refrigerants (Duracool, Freeze 12, et al) and retrofitting to R134 ad nauseam and have found SO MUCH conflicting info my head is spinning. Now a reputable shop is telling me most classic cars they deal with just put R134 into the R12 system using service port adapters and it works like a champ - no retrofitting. Also, I've seen a lot of horror stories about A/C shops replacing the entire system piece-by-piece to remedy leakage that would probably be fine for several seasons like mine. What's the latest advice?

brown7373

I have a 72 Convertible, live in south Florida and mine cools very well with 134A. It had been converted before I bought it and cooling was not so good. I contacted Classic Auto Air for help.

First, I got a POA calibrated to use 134A. NOT the POA update or bypass or anything else. It is an original POA valve. I also bought a crossflow condensor that is designed for 134A. The original condensor is the weak point for converted systems. Although an "expert" can tell it is not original, it is exactly the same size, mounts on the same pins and connects exactly like the original.

I got a new expansion valve, checked and replaced o-rings as required (134A o-rings are different then R-12) evacuated the sytem and refilled with 134A. I get 30-40 degree air from the vents and it does not lose efficiency at stop lights.

I bought a Haynes A/C manual which was very good for helping me understand the A/C system, and it gives step by step instructions on how to do any of the things you need to do. It looks to all but the "expert" as a stock R-12 setup, and it works.

Best of all, I now can do my own A/C work, which is a lot lss expensive thjan using a shop. Not to mention that many shops, unless you get an "old timer", do not understand or have much experience with the older cars. Many just recommend junking everything and converting to aftermarket, totally non original replacement.

hookem horns

I would scrounge around for some old can of R12 and keep topping off for now. If or when one of the major components fail, go for the 134A conversion like mentioned above. I'm happy with the complete Vintage Air system but your car looks way more orginal than mine.

JPMDaddy

Just bought a very original 71 Cutlass convertible and living in Dallas area I know I will need to address all of this to truly be able to drive this car all summer.

@brown7373.. what source did you use for the parts... ie POA and condenser for 134a?

rocketraider

Mike, if you're losing a pound or less of 12 every three years you have a good system. If you can get 12 (it's still out there) I'd stick with it until the system develops a major leak or component failure, then I'd do the same thing brown7373 did.

Don R.

The PO of my Starfire had done a quicky R134 conversion and the system worked when I got the car. I finished the job with the right valves, new receiver / dryer, leak test and full evac and charge. All original hoses, compressor, POA, etc. While not quite as cold as the R12 original it still does a pretty good job in Texas heat and has for two years. I think a lot of places replace a lot of extra stuff on these conversions just to make money.

I do agree with the others though, if your system works and you can still find R12, leave it alone.

droldsmorland

Find the leak and refill with R12. Check the large aluminum nut on the evap line. Thats on the U shaped line up by the fire wall on the evap box. Careful not too tight just good and snug. Spray WD40 on it and move it back in forth 10* in either direstion at most to work the WD into the threads and oring area.
If you convert to 134a you need new O rings throughout, a new or reloaded dryer, new strainer and the right oil which means the system as well as the compressor will need to be drained of all the oil and new oil added then suck it down again. Then you will need to properly adjust the POA valve. Thats the one most miss and why most complain the 134a doesn't work It needs to be adjusted for a lower pressure to get maximum efficiency out of the 134a. You will see a 10* drop with the proper adjustment verses leaving it adjusted for R12. R12 uses mineral oil 134a uses PAG

Miles71

Hi Mmurphy77, if you can still get R12 at a reasonable price, great.

When it comes time to change to Freon 134a, you cannot use your existing hoses!
NOS hoses are 100% incompatible with Freon 134a. It has to do with the size of the 134a molecule, it’s so small, and it goes right through the sides of the old hoses. Only Barrier hoses can be used with Freon 134a.


If you need to make the switch from 12 to 134a, you should replace just about everything in one shot:

All three hoses, Replaced Barrier 134a hoses
POA retuned or replaced with a 134a version.
Expansion valve.
Condenser (The old style will work if not leaking, Most recommend Cross flow style for 134a.)
Evaporator (This is the only part you can keep, If it does not leak).
Dryer (Replace every time you rebuild or full fluid change).
Compressor (Keep if its new enough to be rated for 134a, otherwise replace it)

droldsmorland

Forgot about the hoses and Exp valve. Either Vintage or Classic Auto Air has everything you need that's all they do give them a call and let them guide you. Vintage did an expert job on my hoses dryer etc...Used the factory ends with new hoses.

mmurphy77

I'm having a hard time finding R12 locally anymore. Last time I did it (3+ years ago) there was tons of it on Craigslist. Now all I can find is on ebay and they want a fortune for it. I keep hearing that oem rubber lines that have run R12 in them forever have enough remaining impregnation that they can be used successfully with the molecularly smaller r134a. I guess I'll hold out for the R12 and do what I've been doing. In the event of a major fail/leak/etc. I'll revisit the r134a conversion as long as I can hide it in plain sight meaning correct in R12 appearance. Anybody got a 'line' on some R12 they want to move?

tru-blue 442

If you can find some freeze 12,
it works as well as R-12. You
can use it with the 12, as long
as you still have a vaccume to
pull it in, I used in in the 69 442
after it set for many years.
Worked like a champ.

Fun71

Where did you get the condenser? I'm not currently in the market for one but it would be good to know for possible future use.

Lady72nRob71

Do not mix 134 and 12, or add anything other than straight 12 or proper oil.
It might make it work for a little while, then the system will fail later.

X2
Use the AC frequently to keep the compressor seals lubed.

An original factory POA can usually be calibrated to 134 as long as it works.
I have a post somewhere in here that shows how to cal and test it - easy and cheap to do if you have AC gauges and an air compressor.

Paladin31

Just a little hint there is another option, I have use Dupont R409a refrigerant in one of my old truck systems, it is a drop-in match for R12, 95-96% of R12's capacity and no oil change is required, you can blend with the 12 already in your system, You shouldn't need to adjust the POA valve as the evaporating temperature of 409 so closely matches 12...but you may. Nice thing is the 409 runs about 4-5$ a pound

mmurphy77

I think that was my biggest problem. I hardly ever had to run the A/C over the last year because the weather was very mild.

MDchanic

"Pretty good"?!? That's fantastic!

When our cars were built, replacing refrigerant was considered to be a routine annual maintenance item, and loss of up to a pound a year was considered to be normal and within design limits (see your Chassis Service Manual).

If you're getting away with three years, you're getting away easy!



Sorry, but, No.

R12 molecular size: 5.09Å
R134a molecular size: 5.24Å

R12 is smaller than R134a.

The reason for the nylon barrier layer being placed closest to the inside of the hose, rather than sandwiched in the middle of the rubber, as it was earlier, is because the PAG oil that is required with R134a degrades the rubber over time, and would wreck the hoses before the projected service life of the vehicle was over.
It has nothing to do with the sizes of the respective molecules.



Wow. I was at a flea market recently and picked up four cans for $10 each (less than the $14 that the R134 is going for in the auto parts stores).
The guy had a whole case, but, hey, how much can you buy at once when you don't even have a running car with R12 A/C, right? Especially when you've got a full BBQ bottle of R12 in the shed .



I agree with the others: If the A/C is working well, don't mess with it, just feed it.
And if you do want to make the 134 switch (considering that R134 and R12 will soon be the same price, with R12 potentially going cheaper because of reduced demand), then you definitely need to replace the condenser, the receiver, you should replace the hoses, and you must recalibrate the POA valve.


- Eric

Mike77

30Lb of r-12 is about $1500.00 in Canada. It's illegal to use it or sell. I thought it was in the USA too, as per Montreal CFC protocol of 1997.

Mike

MDchanic

There's illegal and there's illegal.

At a flea market, everything is legal, and nothing is taxed.

Also, R12 is can still be legally bought and sold by certified A/C technicians (It took me about 15 minutes and $20 to get mine from IMACA [now MACS] several years ago), it's just that production is limited in the US (though not "overseas").

You should c'mon down and visit the States more often .

- Eric

mmurphy77

Thanks everybody. I guess I'll be 'hitting' the flea markets.

Miles71

MDchanic, Thank you for correcting me on the Molecular size of R12/R134a (I have been trying to find these exact values).

Attached is a picture of what a stock 1971 CS High pressure hose looks like, 6 months after converting to Freon 134a without changing the hoses to the new Barrier hoses.

If you look closely you will see small oily spots along the webbing lines of the hose. These tiny leaks were on all sides of the high pressure hose. There were well over 200 oily spots on this one hose.

MDchanic

I'm not saying the hoses won't leak with 134, I'm just saying that the reason they'll leak (sooner or later, depending on age, use history, original composition, etc.) isn't because the molecules are smaller, but because the oil damages the integrity of the rubber.

If you then flushed the hoses and went back to R12, they'd still leak after this because the rubber has been degraded - they wouldn't stop leaking because the molecule size is different.

- Eric

jaunty75

Angstrom symbols. I am impressed.