Automotive air conditioning and R12 updates (R134a and more)
What the future brings: new refrigerants
The home mechanic, looking at a can or two of R12 or R134a, may think that government concern over refrigerant is overblown. However, CFCs like R12 have been found high in the atmosphere, where they destroy ozone (since CFCs have been regulated, the ever-widening holes in the ozone layer have been healing themselves). In addition, R134a is 1,400 times as effective at trapping heat as carbon dioxide; a few leaks from a few cars would probably not have any serious impact, but there are an estimated (by the auto industry) 400 million mobile air conditioners out there.
Europe is phasing out R134a due to its relationship to global warming. Carbon dioxide, the current E.U. favorite to replace R134a, is the least powerful greenhouse-gas, but requires high pressures, and is less effective. However, in the United States, the approved replacement is HFO-1234yf. This new refrigerant is dramatically less likely to affect climate change than R134a, and while it will not be required until the 2017 model year, automakers can get greenhouse gas credits from the 2012 to 2016 model years by using it. The new gas was created by Honeywell and DuPont.
R134a, which replaced R12, lives for around 13 years in the atmosphere before breaking down; its “global warming potential” (GWP) is 1,400. 1234yf, on the other hand, breaks up in around 11 days, for a GWP of 4. It was developed to meet European Union directives, which demand a refrigerant with a GWP of less than 150.
Whether HFO-1234yf can be used as a replacement for R-134a is still unclear, but it seems unlikely, as R134a will not be banned; instead, it will have a hefty tax which will prevent frivolous use (e.g. putting in three or four cans a month) and tip the balance for many customers from “frequent refills” to “repair.”
Many have complained about the corrosive effects of R134a and its tendency to leak out of automotive air conditioners much faster than the old R12, which was phased out in the mid-1990s. R1234yf was endorsed by the Society of Automotive Engineers and Japan Automobile Manufacturers Association; a Delphi executive wrote that it was “both a cost-efficient and effective refrigerant option.” It can be used with low-pressure air conditioning systems.
Before R1234yf, there were two major types of air conditioning refrigerant in North America: R12, "the old kind," and R134a-based, "the new kind." (R22 was used briefly as well in the early days.) R12 was dropped due to clearly demonstrated links to holes in the ozone layer, with dire effects for the future.
Air conditioning repairs, troubleshooting, and upgrades
Here is some information from the EEK! list and Allpar's main forums.
The Weisners wrote:
If there was ever a time to get a second or third opinion, it's the A/C business...not everybody is dishonest, but many are. I have had many people bring cars to me who have been told that they need condensers, evaporators, compressors, etc. replaced when all they needed was new O-rings. You can often spot leakage by looking for a oily spots around connections or on condenser coil area, so do a little checking yourself. Have to have a professional do the work but be alert and protect yourself. I would suggest spending the extra money for a new component (when it comes to replacing condensers or evaporators). I've never had much luck with used ones.
Dan Stern wrote:
There are drawbacks to R134a in R12 systems. R134a moves much less heat than R12, which means that your R12 system's effectiveness will be cut. The oil required for 134a reacts poorly with residues that cannot be flushed from a system that has run on R12. This reaction breaks down the oil and frequently destroys the compressor. There are other problems with retrofits. [Note: since this was written, “R12 compatible” oils have been made available.]
- You might get a mechanic saying that conversion to 134a is just a matter of vacuuming the system and putting in 134a. RUN.
- You might run into someone who wants to replace your R12 with "FR-12" or "Freeze-12" or "Frigc." These three (and several others) are simply 134a with an additive that makes it slightly less violently incompatible with mineral oil. RUN.
- You might also get someone who wants to put OZ-12 or HC-12 into the system. These two are blends of isobutane and isopropane. They work very well in R-12 systems, and have no oil incompatibility problems. BUT, they are flammable. To what degree this concerns you is an individual matter.
It's not as clear-cut as you might think, because all refrigerants are blended with oil in the actual system, and all refrigerants are violently flammable under catastrophic system breach conditions (refrigerant rushes out, creating aerosol mist of oil--BIG flameball whether it's R12, R134a, OZ-12, or whatever). These hydrocarbon blends also are cheap (about $1.25 for enough to charge a few systems), BUT they aren't approved by the regulatory bodies for use in auto A/C systems.
Types of refrigerant include:
- "Drop in" A refrigerant that can legally be "dropped into" a system with no modifications required whatsoever. No unique fittings, no oil change, no hose change, no label change. Drop-ins exist ONLY for zero-ODP (Ozone Depletion Potential) refrigerants that do not contain CFCs (e.g. R12) or HCFCs (e.g. R22). This leaves refrigerants that contain HFCs (e.g. R134a). There is a high-performance drop-in for R134a, called Autofrost X7 (GHG-X7).
- "Substitute" or "replacement" refrigerant: A refrigerant that can be used in a system originally designed for something else, subject to "use conditions." Typical Use Conditions include:
- Installation of adaptor fittings. EPA wants every refrigerant to have unique fittings to prevent cross-contamination...this rule was made based on heavy lobbying from 134a industry with a heavy financial stake in having NO alternative to 134a.
- Installation of barrier style hoses (necessary with all non-R12 refrigerants, because the other molecules are much smaller and will permeate through the older nitrile hose material). An industry is springing up in "rehosing" existing hoses with new hose material that has a nylon barrier. Good idea anyhow.
Have lines rehosed once with a good barrier material and never worry about them again. Also get a better-than-OEM front seal in the compressor. Just like hoses, OE front seals aren't great on the typical C171 compressor used on many Chrysler products. Also use neoprene (blue) o-rings in system instead of old black ones, but no problem (same O-rings as used in 134a systems); all this sounds expensive, but not really. Rehosing is the hardest part.
Always use a new filter-drier (accumulator)!
Discussion and alternative automotive refrigerants
SnoMan wrote: Duracool, OZ12a, ES12a and HC12a and R12a (to name a few) are all the same product marketed under different names. It is flammable and so is not accepted by the EPA. All freons are flammable to some extent and R134 will auto ignite around 400F at 5 PSI if oxygen is present, so this flammable thing is debateable and R134 is toxic when it burns.
"AutoFrost" is also known as R406a and it is made up of three different components, 55% R22, 41% R142b and 4% Isobutane (a hydro carbon that is very flammable). It should not really be used in a car system without upgrading the hoses because R22 in not compatable with hoses on cars designed for R12 and they will degrade with time and react with the R22 in AutoFrost. This is not a problem with EC12a like knock offs.
The government/military will not certify AutoFrost for use in vehicles because of the hose issue and it is not a good choice for low dollar conversions unless all hoses are upgraded as well and then it is no longer a cheap conversion.
R22 is a theoretical problem in car systems due both to hose and seal compatibility issues. So is 134. But experience has shown that use of these refrigerants in older R12 systems works due to the hoses being oil soaked enough to minimize leakage. Hose replacement isn't out of the question either. Seals are another matter, but that doesn't seem to be an issue with Chrysler systems to date.
The main reason that car systems didn't use R22 in the past was seal compatibility. Otherwise its temperature/pressure characteristics are ideal for the A/C application.
Lane MacFarlane: 1980s air conditioners
I have quite a bit of personal experience on the A/C on 1982-1988 L, K, and S bodies (having or having had a 1982 Turismo, 1988 Aries Wagon, and 1985 Voyager, and having had to replace evaporators on all three!). All of the above (2.2 or Mitsu 2.6) used a Chrysler/Nippondenso C-171 compressor. This is a dual-acting 3 piston/6-cylinder swashplate type compressor with no pressure controls (EPR valves, etc.). There's a variant of this compressor with variable displacement on some 1990 and later vehicles (I remember a 1990 Voyager/3.0 Mitsu had one).
There were two basic variants to the early C-171, with only the mounting changed. One was the "soft mount" that's on my 82, and it uses rubber isolators and a sub-cradle to mount the compressor. The other was the "hard-mount" that was on the 88 Aries 2.2. The 2.6 and 2.2 "soft mount" compressor appear to be the same (they're the same number in the 4-Seasons book, at least), even though the 2.6 mount is different.
My 1982 has its original compressor and clutch (85K miles), the Aries still has its original compressor (110K miles and another owner), but a second clutch, and the Voyager is on its third compressor (original went out in 1986, that one started seeping oil from the center O-ring in 1996). The basic compressor appears to be quite sturdy, if treated right (don't let it run without oil!), if the system is kept clean (always flush the system if you replace the compressor), and if the rebuild job is good (for a rebuilt compressor, of course).
The real kicker is the quality of the rebuilder, and there's no way of knowing that until the rebuilt compressor crumps! My rebuilt C-171 for the 85 Voyager 2.6 was $110 at AutoZone, no clutch, no problems yet (2 years).
The belt tension appears to be critical, especially on the dual-belt arrangement on the 2.6 (I've gone through two clutches, both having had the bearings destroyed). If in doubt, keep it on the loose side is my advice. As for the system hoses, they're all junk and should be replaced when the system is opened up, with good quality barrier hoses with really well-crimped ends.
R12 To R134a conversion
Bob Lincoln wrote: “To make sure there are no leaks, draw a vacuum for 45 minutes, shut off the pump and see if it holds for 5-10 minutes with no change. You must repair any leak first, so if the compressor leaks, get a junk or new one. If the system wasn't already converted to R134a when you got it, you must flush it with brake cleaner to get the mineral oil out, then use compressed air to purge it. Then you add 2 oz of oil to the compressor, another few oz. in the condenser - no more than 8 total - and button up the system and draw a vacuum. Then you can charge with 12 oz cans until you reach about 85% of original capacity, or proper pressure high and low. You can do it yourself without professional equipment.”
Bob O’Neill added:
If the leak is an o-ring or gasket and not a seal in the compressor then parts will be cheap except for the refrigerant. If the leak is a result of a hard part like a hose or dryer or compressor you're looking at up to $1000 if you take it to have it done.
I will be doing mine myself with the possible exception of charging the system. The compressor, hoses, drier and expansion valve will run me about $450. I will get some of the correct solvent to clean out the evaporator and condenser. Once they are clean and dry meaning no debris or oil I'll then assemble the new hoses, drier, expansion valve and compressor. Once that's done and things are tight it's only a matter then of the vacuum and charge.
Normal sockets are used for most of it and an allen wrench for the expansion valve.
If the hoses are not leaking, they don't need to be replaced. The expansion valve and the dryer should come with gaskets. Get a set of gaskets and o-rings and replace them all on the hoses to the compressor and the evaporator. You may want to use some solvent (proper stuff available from Advance) to pour into the condensor and evaporator to blow out all the stuff left in these. If the compressor is fine you may want to remove it and also drain it of oil. In this way you'll be sure that when the 'right' amount of oil is put in the system it won't be too much which could then lower the effeciency of the overall system.
I've done all 4 of my Daytonas with good results so far.
[If you are] changing most of the components [hoses and such], you'll only need to flush the evaporator and condenser. Unless you're using a solvent that evaporates and leaves no residue, you'll need to evacuate the system better than with a hand pump. The evacuation boils off the liquids and moves them out of the system. I saw it first hand when I flushed my system; I had fresh oil in the vacuum pump and after I finished the evacuation it was all milky and contaminated. I used isopropyl alcohol for the flush.
I'd invest in buying strong vacuum pump, since you never know if you will need it again. If you're conversion doesn't take the first time you'll have to do it again and it doesn't make sense to do it half-baked (again).
As for the conversion fittings, the low pressure one has the needle valve in it and the high pressure one doesn't. You do have to be careful of the conversion kit you buy, something about some are made for GM cars and others are universal for all cars.
One other thing to keep an eye on is the connections at the drier. The aftermarket hoses have the steel tube sticking too far out from the flange and when you tighten the nut down the mating surfaces of the flange on the hose assy. and the drier don't contact properly. I had to take a q-tip and break it in half and stuff the 2 cotton ends down the tube, then I cut the tube a bit shorter with a dremel tool cut-off wheel, filed it smooth and even and took off the burrs around the inside edge of the tube. Once that was all done you can pull the q-tips out and it will drag out all the metal filings and junk.
You will definitely have to change the filter/drier, make sure they give you one that is 134a compatible.
You MAY want to change the expansion valve as well, I say "MAY" because I found that the previous owner of my 1989 had changed the valve and the replacement was specifically marked for 134a. The 1987 with 134a was okay but not that cold (about 55°, where 45° would be normal).
I bought a new Denso compressor and Goodyear barrier hoses from Rockauto, as well as expansion valve and drier.
Now for the procedure. Take out the drier, and disconnect the lines at the compressor and pour the iso down the lines ones at a time then blow air through it with the blowgun and it will all gush out the line at the compressor end (get a bucket). When finished doing both sides (condenser side, evaporator side) put in the new drier (and expansion valve if you do that as well).
Now the most important step - get out the UV light and check the whole system (including the condenser) for any traces of UV dye, if you find any clean them off (iso should work).
Then you can hook up the manifold set and pull a vacuum on the system. Once you have a vacuum for 15 minutes, close off the gauges, close the ball valve and turn off the pump, and let it sit for 15 minutes then open the manifold valve and see if the vacuum held. If it did, close the manifold gauge and let it sit another 45 minutes and repeat; if the vacuum still holds then it's reasonable to think that you don't have any leaks. Then get the vacuum pump going again and pull a vacuum on it for at least another hour (if you have the time go for two hours).
Then put the oil in the injector tool, and use one can of 134a to push it into the system, then disconnect the injector and reconnect the hose and put in 2 more cans. The original charge of R12 was 38 oz at most but when converting to 134a you're supposed to use 10-15% less because of the properties of the refrigerant, so 3 cans is just about perfect.
If the vacuum didn’t hold, you have a leak somewhere. I would still put in the oil with one can of refrigerant and jump the pressure switch so that the compressor runs and cycles the oil through the system, then you can get the UV light out and try to find the leak (this is why you checked/cleaned the lines before hand, so that you don't have any false indications). If you have to fix a leak you don't need to flush the system again after opening it, but you should put back a little oil (depending on how much got expelled) - other than that you repeat the procedure again.
Around here, shops charge through the nose for A/C repair and do the least they can to get your system working, hoping that you'll last through the summer and when it's not working again next year they charge you again and do a bit more work and you have to hope it holds. I'd rather spend the same amount on the tools and supplies as I would on the repair shop.
If you don't have an air compressor, 3-5 CFM is fine for a car.
As for the drier, it definitely needs to be replaced. Also, the compressor doesn't have an internal oil system, it uses the oil suspended in the refrigerant for lubrication. "Draining" isn't an absolute must, but it can't hurt to wash it out with the iso, so long as you remember to lube it up with some 134 oil before you put it back in. I've never flushed any of my compressors and have had no problems.
Much more information is on our forums.
“88daytona” wrote: “The guy at Polar says that the A590 compressor units fail sometimes by letting the threads corrode in the rear housing causing the bolts to loose their torque value. Then the body will leak, he says it is pretty common because of the aluminum body and steel bolts. The seal and gasket kit was $40.”
Additional historical and R22 notes
Mike Sealey wrote: The earliest Chrysler trunk mounted A/C systems (around 1953-56) used R22, probably because Chrysler's Airtemp Division made home and commercial A/C units which used R22. A/C units from 1957 on appear to have used R12, and were sourced from an outside supplier (Eaton, Yale & Towne in most older models) despite use of the Airtemp name. Some 1957 MoPar owners' manuals refer to the factory A/C units as "Cartemp Air Conditioning," apparently to differentiate the two systems.
In the early days, automotive air conditioners did not cycle the compressor, as they do not — shutting it off periodically to avoid freezup or to save power — they had it on all the time. John Wood wrote:
The very old systems never cycled the compressor (except when the AC was first turned on). These units had a small clutch surface area that was never made for a high duty cycle. Freeze up control was handled by bypassing the evaporator using a few style of valves (POA, STV, or HGB). Passenger compartment temperature was controlled by mixing in heated air from the heater, and, to some degree, by mixing in outside air.
There were a few different designs, but a common one was to have a temperature sensing, coiled wire, that extended into the evaporator from a by pass valve that was thermostatically controlled to open and close. When the valve began to open, refrigerant bypassed the evaporator into the accumulator. This was essentually the regulator to prevent freeze-up. The accumulators were fairly large. The systems were great but all the individual components added up to a lot of weight.
... a higher speed fan setting caused more heat to pass through the evaporator and be absorbed. The heat sensing wire ... closed off the bypass valve so that more refrigerant would pass through the evaporator and provide more cooling capacity. That is how the original systems avoided cycling the compressor. It was not the most efficient system but we were not so concerned when gas was 25 cents a gallon.