It's getting hot quickly so I need to fix the A/C on my 70 Valiant. Is there any problem with using R134 in this system? The A/C shop seems to think there is some sort of valve in the compressor that will prevent it. Any ideas? I know someone that put 134 in a 68 Valiant with no adverse affects. Cost is the limiting factor since R12 is $55 a pound and it takes almost three pounds to charge. Also, my compressor has a front pump seal leak. How hard is that to repair?

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70 Valiant Super Six

Front pump seal is a very easy fix on the V2 compressor. Remove the clutch assembly, remove a few bolts and the seal's in your hand. The A-body did not get the EPR valve your shop is worrying about until 1974, so no worries there. If you're intent on doing an R134a changeover, remember you need to get the old oil out of the system—not hard to do by simply draining the compressor sump and flushing the system—and you will lose some cooling capacity, especially under high-demand conditions (low engine and vehicle speed/stuck in traffic). Head pressure will also be higher, which means greater torque load on the engine from the compressor and greater stress on all high-side junctions and seals.

To compensate for the efficiency loss and bring head pressures back down, spend the extra $130 for a new parallel-flow condenser. These are very much more efficient than the serpentine type you've got now, greatly increase system performance and greatly reduce head pressure.

Of course you will also need a new filter-dryer. Make sure it is R134a compatible.

Sure, it's tempting to go the quick and cheap route (suck out the R12 and dump in the R134a), but the short-term consequences of reduced A/C and engine performance and the long-term consequences of system damage aren't worth the dollar savings.

DS (licensed A/C tech, nonpracticing)

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

DS - I've read somewhere that filter/driers can (must) be "rebuilt" after the system is opened for an extended time. As you know early A Bodies used a f/d that input at one end and output at the other, making them kind of unique. How true is that statement about being rebuilt as I doubt they are still available in the original configuration?

Yeah, the horizontal filter-dryer for the up-to-'66 A-bodies is N/A. There are others very similar in size, shape and format that can be used, or—yes—the originals can be rebuilt by a few different companies. On my '62, I've got a later-type (vertical can) filter-dryer. It's not in a very good place (I didn't do the initial installation) and there's a bunch of flared copper tubing and a weepy serpentine condenser I want to get rid of. When I rework this, I'll probably put a new vertical-can filter-dryer mounted to the front of the radiator support panel, just to the side of the condenser. Clean and out of the way!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Hey Dan, what about this Freeze-12 stuff that they have came out with. Does it work better than R-134a?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Some non-spec "replacement" refrigerants are safe and legal—subject to usage conditions (more later), but it's really not a good idea to use them. Freeze-12 contains 80% HFC-134a and 20% HCFC-142b. It is similar to other R134a blends such as FRIGC FR-12. They are roughly as efficient as R134a, but its oil miscibility and compatibility are poor. This isn't as big of a deal on systems with positive lubrication of the compressor (such as the Chrysler V2 system) but it is stil problematic. The way the A/C system is designed, oil actually mixes with the refrigerant and is thereby carried throughout the system to keep the seals, valves, compressor, etc. "wet" and lubricated. If a refrigerant with poor oil miscibility is used, the oil doesn't mix with the refrigerant. Instead, it just gets "swept" (pushed) along by the flow of refrigerant, and settles in the lowest points of the system. This not only starves higher parts for oil, but also hurts system performance due to the puddles of oil blocking passages at the low points.

There are other issues with "alternative" (non-R12, non-R134a) refrigerants. Because they are blends of different-size molecules, a leak causes the different molecules to leak out at different rates. This upsets the percentages of different constituents in the blend, and can really spoil things. Not just performance, but also oil carrying, head pressures, etc. And once that happens, you can't just top up the system, you have to completely empty (evacuate) it and recharge from empty, to ensure the correct blend percentages.

And that brings us to an even bigger problem: service facilities. There are a lot of "alternative" refrigerants out there. Finding a shop that works with any particular alternative refrigerant is a hit-and-miss deal. You might call around (or look on any particular refrigerant's propaganda page) and find a local shop. Now: What happens when your A/C suddenly needs service and you're far from your home shop, or your home shop changes to a different alternative refrigerant? Most shops will not touch a system that's been charged with other than R12 or R134a. Those that will, really hate to deal with an alternative refrigerant other than the one they've chosen, and they charge $$$ for the nuisance. ALL automotive refrigerants must be recovered (they can't just be vented out into the air), so a shop would have to have a recovery machine for each and every different refrigerant. Mostly they don't bother.

Now, what about those "usage conditions"? They're legal requirements for the use of any refrigerant other than the one the system was designed for. They include such things as installing barrier hoses and permanently installing special fittings—different and unique for each and every different alternative refrigerant. Legally speaking, there is no such thing as a "drop in" replacement for R12 Freon.

(All non-R12 refrigerants have molecules smaller than R12 molecules. These non-R12 molecules are small enough to leak through ordinary hoses. "Barrier hoses" are new-type hoses designed with a nylon liner inside to prevent small molecules from seeping through.)

Marketers of "alternative" refrigerants often tend to downplay (or keep completely quiet about) these requirements. They are not optional!

If despite all this you are determined to use an "alternative" refrigerant, there are better choices than Freeze-12. AutoFrost has done well for me in various Chrysler systems, in part because it is not based on R134a chemistry.

Really, though, there's no very good reason to use anything other than R12 or R134a. The former is what our systems were designed for, and it's what works best in them. In the US it's still legal to use. Sure, it's expensive, but you don't need much, and on a system in proper repair, you won't need any more for a long, long time. My '62's A/C system has gone 10 years without needing any topping up, and it's an olde-tyme system full of leak-prone design (flare fittings instead of O-ring, etc.).

If you decide you just can't cope with $40/lb for R12, and you're bound and determined to convert to something, go to R134a, which is the current standard refrigerant. Don't be tempted by the $20 "retrofit kits" you find at the parts store; they are known in the industry as "compressor death in a can". They work in the short term—at reduced system efficiency—but over the long haul they can do very extensive/expensive damage to A/C components.

The cost of changing over to R134a isn't just a question of $X/lb for R12 vs. $Y/lb for R134a. To do a 134a conversion the right way, you do a complete system flush and drain. You replace the compressor shaft seal and all system gaskets and O-rings (non-Neoprene seals WILL leak with anything but R12!). You cast a very critical eye on all the hoses in the system, and have anything even remotely questionable re-hosed with barrier hosing. You spend the $100 or so on a parallel-flow condenser. You install a new, R134a-compatible filter-dryer. Then you install R134a-compatible oil and charge the system with the correct amount of R134a. Then, you're all set to go for the long haul.

One kind of "alternative" refrigerant merits special mention: Hydrocarbon blends. These are blends of isopropane and isobutane. They're sold under names like EnviroSafe, HC-12a, OZ-12, MX-12a, ES-12a, HC-12a, ("anything"-12a). They're inexpensive and widely touted as "drop ins" (see above!)

Do they work? Yeah, they work.

Is it safe? The sellers say yes, but can't seem to provide enough supporting data, despite 15 years of trying, to pass the refrigerant safety tests ALL refrigerants are required to pass before they're legally approved. See here. The sellers claim it's due to politics and Big Refrigerant Inc's desire to own the market. EPA says Don't. MACS says Don't.

(One argument commonly advanced for these refrigerants is "You carry 20 gallons of gasoline and you don't worry about that, so why worry about 2 pounds of hydrocarbons in your A/C system?" The answer is that the fuel system is specifically designed to store, carry and transport flammable fluids. The A/C system isn't.)

if you mouse around on the websites selling this stuff, you'll find them talking about "legal 2nd-generation drop-in" refrigerant. This is a bit of doublespeak. Here's how it works: It's illegal to replace R12 with hydrocarbon refrigerants, but it's not illegal to replace R134a with hydrocarbon refrigerants. A law against the latter was never written, 'cause there's no reason why anybody would ever replace R134a with hydrocarbons. Unfortunately, that legal omission is being treated as a loophole by those selling hydrocarbon refrigerants. The idea, they say, is to convert your system over to R134a (which is legal), then replace the R134a with hydrocarbons. Nudge nudge, wink wink, elbow in the ribs, and if you happen, wink wink, to forget the "change to R134a" step, wink wink, why, that would be awful. Wink wink. Just terrible. Wink wink.

As a final note, A/C shops have sniffers that detect what the system you bring them is charged with. When they detect a nonstandard refrigerant, they will either tell you to leave or start making the cash register ring Large. If they detect hydrocarbons, they will usually tell you very quickly to get the hell out of their shop.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan, excellent post. I concur fully. I have pretty much, given up posting A/C info on auto related forums. Seems like everytime I do post, I get replies such as, "you don't need to do that" or "you can do this", from people that don't know what they are talking about.
I would like to add a couple of things.
1) Only use pure R134a or R-12. Do not get the cans that have other compounds in them. ei "sealers", "cooling boosters", oil, etc. Dye is ok, but only 1 can per system.
2) Consider the fact " if the compressor is replaced with a new or reman. unit, the warentee will be void, it anything other the 134a or 12 is used.

PS: I am a ASE master auto tech, my speciality is A/C, with over 40 years experiance in residential, commercial, industrial, and auto HVACR.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

How about the evaporator under the dash? Does it need to be upgraded along with the condenser?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Naw, the evaporator's fine as it is.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Excellent and very informative post Dan. As was stated by Charlie_S, often you get opinions and not facts. Cost has been my only roadblock but you make a very valid argument. The compressor seal scared me but I'll give it a shot. The link for the parallel-flow condenser was great also. The one I have now leaks. Thanks for the insight.

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70 Valiant Super Six

Glad to help out, 70S. Shaft seals are not hard to replace. I assume you're working with a Chrysler V2 compressor? Very easy to remove the clutch, then just four or five bolts have the shaft seal retainer off and it's a simple remove/replace deal from there.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.