That is the question. My '69 R12 A/C system is blowing less than cold air, and I still have a couple of weeks before the weather turns so cool that it will become difficult to assess the results of whatever I decide to do. I've done a lot of online reading about R12a as a substitute refrigerant and even ordered enough Red Tek 12a to do a full recharge. I probably could make do with 12 oz. cans of R12 from eBay, but at $35 per can I'm not real enthusiastic about that.

The idea of HC refrigerant doesn't bother me a bit from a safety standpoint. It's been used around the world for decades, and is widely used in Canada where R134a is unavailable to DIYers. I also know that R134a will soon go the way of R12, not to mention the higher required pressures (more stress on old parts) and required oil change if I wanted to go that route.

FWIW, I have my own gauges and vacuum pump that I use on R134a systems and am perfectly capable of doing this myself (with the exception of evacuating the R12).

Any thoughts, opinions, or experiences anybody can share about this?

 

if the system was opened it can cause a problem with the evaporator, corrosion etc first of all so that is a consideration. no2 if the reciever dryer is being replaced anyway why not go the 134 route if the cost can be recouped from the r12, in the future the price for r12 only increases. i have a vi---e system in mine and it works quite well and is very light. i saved about 50 to 60 pds over the old system.

 

For what it's worth when I replaced the compressor on my 83 H/O I put the r12-a back into the system. I evacuated the system and installed new receiver drier and new orifice. The new system does a fantastic job. I had previously used the r12-a in a 93 corvette and it worked just fine. I don't think I would try mixing it with other numbers though. I would only use in a clean dry system.

 

i have a bunch of r12 for 20 a can for 12oz and 25 for 14oz...

nothing works as good as r12 period..ive tried it all over the years...it just works..

 

I charged my sons 92 Nissan sentra S-ER (which is an incredible car by the way) with R134 and it works so-so. As long as you are moving ie. Air through the condenser it works fine. But the longer you sit at a stop light in the bakersfield heat it feels like you lost the entire charge. Once you start moving again it starts to function normally again. I think the r134 is not as efficient as the r12 and the pressures run too high for the r12 calibrated pressure switch. Adversely I charged my older sons 88 acura with freeze12
and it worked perfectly. Just my experience with the two... Am considering charging the Nissan with freeze 12.

 

R12A is a hydrocarbon that is extremely flammable. You might recognize it by its more common name PROPANE. It will contaminate your entire system, and once contaminated, everything will need to be replaced, if you want to convert it back. The problem with R134A is that the smaller molecules of the gas, can penetrate the old rubber hoses, and that you also need to change the oil, flush the entire system of the old oil, and re-hose the entire system with barrier hose, if you want to do it correctly. With air conditioning, there are no short cuts, and using the wrong products devalues your car. It is your car, and you are free to do as you like, we can only advise you. I have seen how volatile an engine fire can be when the air conditioning hoses burn through, and the oil in the refrigerant lines starts to burn. It is like a flame thrower. I can image the same scenario with PROPANE in place of the R12 or R134A refrigerant. I can hear it now, when the flames hit the PROPANE, the flames will travel through the hoses, and all the a/c system will go BOOM, like a hand grenade. Don't want to be anywhere near when that happens.


http://www.epa.gov/ozone/snap/refrig...12alng.html#q2

 

All good points, and I appreciate all of the feedback and suggestions.

I don't see a conversion to R134a as a good option. As gs72 and Junkman pointed out, the operating pressures are higher, the molecule size is smaller, and it's less efficient than R12. None of these things bode well for a 46 year old A/C system. Although my compressor at some point was replaced with a 4 Seasons compressor and the receiver/drier and expansion valve have obviously been replaced (probably at the same time as the compressor, although this was before I owned the car), the rest of the system is original. When it had more of a full charge, it worked pretty well, and with all of that being the case, I would prefer to keep it as original as it currently is. The compressor runs smooth and quiet, and I've pretty thoroughly checked the system for leaks with a halogen detector and found none.

So I think my only real options are:
1) To keep it R12 and bite the $$ bullet for as long as I can.
2) Change it to R12a, even though, as Junkman pointed out, HC-12a (R12a, Duracool, Red-Tek, Envirosafe, etc.) is not EPA-approved and use of it in any motor vehicle A/C system is considered illegal.

I do find it interesting and ironic that although the components of R12a are entirely non-environmentally damaging, and it is far better for the environment than R134a or any other CFC refrigerant, it is the EPA that is blocking its legal use because they don't have the required paperwork. But that's bureaucracy at work, and if I do choose to use R12a, I don't anticipate the Feds knocking on my door with a warrant.

R12a/HC12a does run at lower pressures than R12 and it has larger molecules, which may make it slightly less prone to leakage. And although it is comprised of flammable gas components, the full charge in my 4-lb (R12) system would be 21.3 ounces. That's just 1.5x a hand-held propane torch or stove bottle. I do believe that responsible use would require regular inspection of A/C hoses and fittings, but I don't consider it a huge risk (am I wrong?). Other than the flammability factor, propane and isobutane are excellent refrigerants.

Junkman, that's a good point regarding contamination of the system if I use R12a... But I can't see any reason that the R12a could not be evacuated at any time and the system returned to R12. The oil doesn't even need to be changed. What components would need to be replaced, and why? A fill and purge with CO2 or N2 should remove all traces of the R12a.

Devaluation of the car I definitely can see, considering the amount of controversy, although I have no intention of selling the car. I guess I need to weigh the value (to myself) of a working A/C system.

marxjunk, I might take you up on a few of those R12 cans. I threw away my old R12 can tap valve/hoses a few years ago, but I expect I could find a new one somewhere.

 

Recharging with 12 is the best. Converting to 134A is not hard and it does work well. I have to charge my car converted to 134A with two cans every seven years. I just recharged it, and it did very well this past weekend.

 

If there is no oxygen in the system, how would that happen?

 

Quote:

Originally Posted by Leadfoot

Junkman, that's a good point regarding contamination of the system if I use R12a... But I can't see any reason that the R12a could not be evacuated at any time and the system returned to R12. The oil doesn't even need to be changed. What components would need to be replaced, and why? A fill and purge with CO2 or N2 should remove all traces of the R12a.


The oil will need to be changed out, because it will have absorbed some of the R12A refrigerant, as well as the receiver/drier. I don't know how much residue would be left in the walls of the hoses, and it might or might not cause a contamination issue. I would also recommend using a flushing compound to clean out the evaporator and condenser, no matter what you decide on for a refrigerant. Proper flushing will assure you of a better end result. Many people don't do this, and some get lucky, and everything works out well. I hate having to do the same job twice, because I took a short cut.

Devaluation of the car I definitely can see, considering the amount of controversy, although I have no intention of selling the car. I guess I need to weigh the value (to myself) of a working A/C system.


All cars are eventually sold, even if it isn't going to be you. I have no intentions of selling any of my cars, however, I realistically realize that even if my wife were to keep them, once she is gone, they will be sold. Once I am gone, it doesn't matter much how much they are sold for, since I will not benefit from the sale.

marxjunk, I might take you up on a few of those R12 cans. I threw away my old R12 can tap valve/hoses a few years ago, but I expect I could find a new one somewhere.


You can find hoses, gauges, and can taps at just about every swap meet you go to. You can also buy them inexpensively from Harbor Freight, and they will be fine for occasional use. I also see both new (China made) and used gauges sets on eBay all the time. If you buy a can tap, the best one to buy today, is the type that go around the side of the can, and puncture the container. Many of the older R12 can tops are good until you put pressure on the seals, and then they will leak. I prefer the side of the can taps for this reason.

I will attempt to answer some of your questions. As for going over the system with a halogen detector, I have done the same with my wife's car, and couldn't find the leak. I finally gave up on the detector, and put dye into the system, and found that the leak was at the point where the hose was crimped to the fitting. The slightest air movement is enough to "blow away" a very subtle leak, but one that keeps draining your system over a few weeks. I also had a problem with my 1962 Chevrolet system, which developed a leak at a hose clamp fitting. I though that would be an easy fix, just by tightening the clamp. Unfortunately for me, it turned into a complete re-hose job, since I found that the 53 year old hoses have become so hard, that they no longer fit snuggly over the barbed fittings. I am now in the process of replacing all the hoses on all of my cars, where the Freon has leaked, with modern barrier hose. I am also replacing all the old "O" rings with the newer green "O" rings, including all those in the compressors. Sure it is going to take more time, but with the high cost of the refrigerant, in the end, it will save me both money and time.
As a side note, you can purchase the Delco 525 viscosity refrigerant oil from Amazon. It sells for about $15 a quart.
If you decide to do as I am doing, and replace all your refrigerant hoses, your local hydraulic hose shop should be able to cut off the crimp fitting, and remove the old hose and crimp on the new hose. My local shop didn't have the barrier hose, so I purchased 25' rolls on eBay inexpensively, and they installed my hose onto the old fittings. I sent my original receiver/drier to Classic Air in Tampa, and they cut it open, and installed new desiccant. I also sent them my expansion valve for testing and re-plating, and it looks just like a NOS part. It all depends on how "original" you want your car to look.
If you want to use R12 or R134A if you re-hose your car, I suggest your going to swap meets to find your refrigerant. This past summer, I picked up some R12 cans in price ranging from 2 cans for $5.00 to $12.00 per single 12 ounce can. I was even able to get a partially filled 30 pound cylinder inexpensively. The guys that think it is gold ask a lot for it, and the guy that just has a few cans that he wants to turn into folding cash, are willing to let it go for a reasonable amount.

 

 

Sorry, but after two repetitions, I have to respond to this.

R-134a is a molecule with two carbon atoms attached to each other, with four fluorines and two hydrogens attached to them.
Its diameter is 5.24Å.

R-12, with only one carbon, two fluorines, and two chlorines is smaller.
Its diameter is 5.09Å.

R-12 weighs more at 120.91, versus R-134 at 102.03, so R-12 is heavier (because those chlorines are heavier than those hydrogens), but that has nothing to do with what you're saying.

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.



The video posted does not address the situation in which a hydrocarbon-filled refrigeration system is breached, but instead addresses the situation in which a sealed tank of propane is heated by an independent fire, which ultimately causes an explosion of the sealed tank.

In order to have an explosion, you need to have a sealed container, so that the internal pressure reaches a point where the container's structure fails suddenly and catastrophically, resulting in the release of the pressure over an extremely short period of time.
This is why black powder, when poured in a pile, will go "FWOOMPH!" but when sealed inside a length of pipe will explode. It is also why gasoline tanks generally do not explode (sorry, movie fans).

In the case of an automotive A/C system, the most likely outcome of a breach of the system caused by an accident, followed by ignition of the propane inside due to a spark, would be a sustained flame issuing from the site of the breach, which would have the same effect as though you placed a propane torch in that area of the engine compartment - it would cause a fire.
Now, as that flame and the subsequent fire burned, they could melt other tubing or hoses, leading to the release of more propane, and further spread of the fire, possibly including a BLEVE (I love BLEVEs), or Boiling Liquid Evaporating Vapor Explosion, which occurs when the liquid propane (which is non-combustible) flows out of the system onto the ground, then flows along the ground, releasing a cloud of vapor above it as it does so, which is burning, or ignites, causing a fireball, which can be some distance away from the original source of the leak.

- Eric

 

Thank you for your explanation of the molecules and the fire. I stand corrected and have learned from your explanation.
Thanks again
Junk...

 

You're welcome.

No offense intended - it's just that all of us here try hard to stop inaccurate information before it starts, so that it doesn't get a leg up (I think we're the only site on the interwebs to do so. ).



- Eric

 

One thing that can happen is that, as you run out of a fuel from a pressurized source, is that the flame will propagate back up the hose as the flow stops. If you've ever cut the propane off at the tank, or ran out, on your grill, the flame gets smaller and smaller, then goes "whumpf" at the end as the oxygen gets up the hose and it all blows out. Very small explosion though. However, until that point, the flame will simply keep going at its location unless it melts something critical, like Eric says.

If that happens, often times the gust of gas blows the flame out. I did that with a bic lighter once as a kid. I took the valve off, and it was leaking through its metering orifice and couldn't be corked. So I took it outside, lit it, and had a nice little flame on the plastic. Pointed it away, and let it burn. It melted through the orifice and turned itself into a rocket. I believe it left the property under full thrust, horizontal flight, at approx 60 mph, and went into the woods. Point being, the flame was out once the flow blew it out.

 

Very interesting. I'm enjoying the discussion, and thanks much, Eric, for keeping things correct, as well as for the excellent explanations.

Koda, Junkman, and Eric, you all got me thinking that while the total amount of flammable gas in the system would be relatively small, in reality, very small amounts of propane and isobutane can burn for a very long time. I don't use a propane torch often... but I've been using the same bottle of propane torch fuel for at least 10 years. Unless I'm sweating big copper fittings, I rarely turn the valve more than 1/4 open. And that's still a very hot flame from a very small amount of gas. Granted, a leaking A/C system hose is not a propane torch nozzle, but this is still food for thought.

What's probably more troubling is a statement I found by the SAE (2005, I think; I need to go find it again) which expressed a valid concern about the use of HC refrigerants in systems not designed for flammable refrigerants. Although the SAE could have an underlying, less than altruistic interest in keeping HC12a out of American vehicles, and the rest of the article was largely self-serving, I think it's very difficult to argue against the logic of this statement.

I still think a catastrophic fire or explosion involving HC refrigerant is very unlikely, and a crash large enough to cause such an explosion would most probably be something nobody would walk away from anyway, fire or not. But freaky and unlikely things happen every day.

So, I seem to now be leaning strongly towards sticking with R12. I'm going to need to stock up a little for the future.

 

Cheeze...now I have to clear out another corner of my brain to accommodate this new wealth of information. It's getting crowded in there.

 

Thanks, but that is mixed with outside air. I was talking about the comment on the flames traveling inside the propane hoses, which would be isolated from outside air. The explosion I was expecting followed a leak of the flammable gas, which allowed it go mix with oxygen before the combustion.

Not that I'll be trying it

 

you guys make stuff so complicated..

science lessons...whos right; whos wrong..this threads a drag....all ya had to say was

dont use the propane..its dangerous and you can get blowd up...

and we could move on to serious things...like extra cheese or mushrooms on the pizza i want to order.....

 

Both.

Life's short.

- Eric

 

And then there's the 20 gallons of gasoline to worry about. How do any of us survive with all this dangerous stuff around us?

 

R-134a conversions are quite common on vintage cars, and I don't see it causing any devaluation. My buddy had his '68 442 converted this spring, and he was told that if he had stuck with R12, then a recharge in a few years would be $600-$700.

 

Where? At ScrewYouGood Motors?

At this point, I've been seeing cans of R-12 reliably selling for about $20 at car flea markets, with the occasional deal of $5 or $10.
Since leakage of up to a pound a year is said to be acceptable in the CSM, and well-maintained systems leak much less than that, $20 a year in freon would probably be on the high side.

- Eric

 

Why do you think E P A was so intent on getting rid of it? There are car-haters in the world who will try anything to get people OUT of their private cars and INTO public transportation.


These knuckleheads have invariably lived in large cities their whole lives and have no concept that some of us live in areas where public transportation is non-existent.


I also believe that the big reason DuPont pushed 134a is because the patents (i.e royalties) were expiring on 12.


If you can get 12, keep using it. It's the safest and most efficient option in the long run.

 

This sounds pretty crazy to me, too. I haven't been following the R12 market very closely, but others who do are telling me that R12 prices have been falling for several years due to much lower demand. It seems that many 'experts' expect this trend to continue until R12 availability reaches the hen's teeth stage. Interesting economics at work there.

The A/C section of my factory service manual is a pretty interesting read 47 years after inception. I'm sure it must draw serious gasps from the EPA and probably fainting spells within the Greenpeace crowd. (Not that I'm completely unsympathetic to their causes.)

--JP

 

My continuing research has led me to some interesting info. This is from Mainstream Engineering's EPA Section 609 certification manual (sorry for the long quote):

"Propane and butane is used in Europe for air conditioning applications and is more closely related to the saturation pressure temperature curve of R-22 but because of their flammability, the MVAC system must be designed specifically for their use. Flammable refrigerants pose a special challenge and these system must be designed to protect users, service technicians, and disposal personnel from the possibility of fire. MVAC systems in the USA have not been designed to use flammable refrigerants. In general, hydrocarbon-based refrigerants are flammable. Clearly, the use of flammable refrigerants in existing systems, not designed for using flammable refrigerants, can pose a risk not found with nonflammable fluids. Currently, the following 18 states and the District of Columbia ban the use of flammable refrigerants in MVACs: Arkansas, Arizona, Connecticut, Florida, Idaho, Indiana, Iowa, Kansas, Louisiana, Maryland, Nebraska, North Dakota, Oklahoma, Texas, Utah, Virginia, Wisconsin, and Washington.

"Although new systems can be designed to safely operate with flammable refrigerants, none of today’s systems are designed to do so. Demonstrating that a flammable refrigerant can be used safely in current systems, whether existing or new, requires a comprehensive, detailed, scientifically valid risk assessment. EPA has required a risk assessment for flammable refrigerants since the inception of the SNAP program in 1994. An assessment must address potential leak scenarios such as collisions, servicing errors, and disposal procedures. In addition, the assessment must consider ignition sources ranging from cigarette lighters or matches to sparks caused during a collision."


Here's a link to the actual www site:
http://www.epatest.com/609/manual/609_section2.html

 

1234yf, the new stuff, is flammable, and is going into some new cars now.

 

Exactly. I remember back in the 90s after R12 was phased out it was going for $50 a can, and now it's around $20. Seems there was so much left out on the market due to all the R134A conversions that the price hasn't gone up as we were told it would. I think it's currently the same price as it was back in 1999-2000 when I decided not to do R134A and stay with R12. I was told back then to stick with R12 until it became too expensive, and at that point think about doing a conversion. And now 15 years later we're not at that point yet.

 

DIDO! My dad was saying this about Dupont, back 25 years ago. I remember 1992 being a crazy year for brand new a/c car. Some models had R12 and some R134a.

 

For the record Jerry's (toro68) dad owned an auto A/C shop in Portland ME for many years.

 

So, with all of this great feedback, I've answered my own question (my answer is NOT r12a. I'll stick with R12.)

I have a new 20lb tank of R12, a new receiver-drier, and new Schrader valves. I thought it best to go ahead and replace the old valves, and since I'll have the system open for that, I'll replace the receiver-drier which is probably overdue anyway.

So my new question is: is there a better way to access the receiver-drier on a 69 than through the bumper and grille? I tried removing the grille and found that I apparently couldn't do so without first removing the bumper. That seems a little crazy, but I couldn't find a way. I could access the receiver-drier from above, but that's a whole 'nother can of worms. Any suggestions?

 

No suggestions, I remember it being a PITA.

One question: where did you get the Schrader valves? I need new ones.

 

Fun71:
I got the Receiver/Drier and the Schrader valves from Rock Auto. The valves are in Four Seasons kit #26777 with replacement service port caps, which I also needed. The local Auto Zone stores had the same kit in stock for a slightly higher price.

If you just need a couple of valves, send me a PM. I think I have a bunch of extra new ones now. I'll check what I have this weekend against the original ones to make sure they're the same.

 

While you have the system open, you might as well change out all the "O" rings to the new green "O" rings that are not as effected by lack of oil saturation during the off season lack of use. I am in the process of resealing my entire A/C system including all the "O" rings in the compressor. I am sticking with the "old fashioned" ceramic front seal. The Corvette website has a good tutorial about compressor resealing procedure. http://www.corvetteforum.com/forums/...placement.html

 

That's a good read on the compressor seal replacement. Thanks for the link, Junkman. I remember having to do that job many years ago without any of the special tools, and it wasn't a lot of fun.

As for the O-rings, I'm not planning to open my system that far. I haven't found any leaks anywhere, and my compressor seal is not slinging oil. I don't know when the system was last fully charged. Could have been three years ago or twenty. When I recharge, I'll add some UV dye and keep an eye on things. At least I'll have a known date when the system was charged.

Does somebody sell those new green O-rings in complete sets, or does a person need to track down the quantity and sizes of every O-ring in the system?

 

I swapped mine out to the green ones last time I had the system open, and from what I remember there were just a few as most of the connections are compression fittings. I matched up what I needed at the local parts store.

I sent you a PM abut the valves.

 

I bought a package of the green "O" rings from Classic Air in Tampa, and I got my green "O" rings for the compressor on eBay. Changing out the smaller "O" rings shouldn't take very long, and it is cheap insurance.

 

I obviously need a much better anti-MAW helmet...

When I had the system evacuated and replaced the receiver/drier, the old oil collected resembled 40 weight mixed with coca-cola. Although a very close examination revealed no metal particles, something clearly has affected the system oil in a pretty ugly way.

Further, when I decided to replace the service port Schrader valves, the old high side valve came apart, with the body of the valve stuck in the port. I could not manage to remove it without damaging the port body. So my plan has changed. Right now the system is sealed up and holding at 5 psi, with nitrogen in place of R12, while I wait for new parts to arrive.

At this point, I think it's prudent to replace some of the 46 year old original stuff just because it's gotta be getting tired (like the port valve). I will not convert to R134a, but whatever hardware I replace will be R134a compatible, even though, for the time being, I see no good reason to convert to R134a.

I have a new (3) hose set and O-rings on the way from Original Air and a spare (new) receiver/drier on the shelf. I'll also replace the compressor. Although the Four Seasons A6 compressor that's in the car now seems OK and doesn't (measurably) leak oil or refrigerant, it's at least 25 years old, and now is a good time to replace it. I'm thinking the new compressor will be a Pro6Ten from Old Air Products. Keeping things 100% original under the hood has become a lot less important to me than having a system that works and lasts. I haven't ordered the compressor yet, so any comments or opinions about this are very welcome.

I'll flush the system, and as long as I'm replacing things, I'll replace the TXV. Does anybody have an opinion on the $15 Four Seasons TXV available from AutoZone vs the $60+ TXV from Old Air and others? Is this just a case of price gouging, or is there really a price-justifiable difference?

I'll test the POA valve, and I'll keep the original evaporator and probably the condenser. MAW issues may change my mind about the condenser, but I'm convinced that both coils are still in good condition, and a good flushing should be all they require.

Any opinions from you wrench heads who've already gotten into this are very welcome.

Incidentally, this thread is no longer about R12a...

 

I know this is an old thread; however, I'm considering updating the AC on my new 86 Ford f250, pics to come for those who care. Once I update the AC on my truck, I would also update the AC on my Olds.

Apparently, R12 isn't cheap:
http://www.ebay.com/itm/R-12-Refrige...tXSvYt&vxp=mtr


Here is an r12a kit:


I'm wondering, if I flush the system and replace the hoses and drier would there be any reason to run a "stop leak" product through the system? Here is a flush kit:


I'm not concerned about the flammability of r12a. If it's good enough for Canadians and Germans it's good enough for me. I'm not concerned about EPA regulations either. However, I wouldn't rule out r134a if there was way to convert my system successfully.

I want to make sure the time and money I put into a system conversion would have good results. I already know that r134a does not cool sufficiently in a r12 system. I put r134a in the AC system of my 90 Buick Estate wagon years ago and it never worked very well. Is there a way to use r134a without buying a completely aftermarket system (i.e. Vintage Air)? I've heard that r134a needs an oversized evaporator if you put it in an r12 system. If so, how do I determine what size evaporator would be needed and where do I buy it?

Thanks for your input.

 

I find r134a to cool sufficiently in an r12 system. It does not cool to original specs, but it does work. My vehicle with r134a in a r12 system was converted in 02, needed a charge in 09, and a charge in 15, and it will put out mid 60s air on max on a 100 degree day. It should be putting out 30s or so, but it does work enough for me.


It will go back to R-12 during a restoration some years down the road.