My recent post on the 1953 Chrysler Airtemp air conditioning system and its rather unusual R-22 refrigerant spawned a little confusion over various A/C refrigerants, so I pulled together this post to explain this topic more fully than I was able to in my Chrysler post.
All air conditioning systems rely upon some sort of refrigerant to undergo a phase change between gas and liquid (and back again) to remove heat from the area being cooled. The earliest A/C systems used a wide variety of refrigerants like ammonia, chloromethane, propane, and sulfur dioxide. None of these compounds were really suitable for automotive use, as they are all either flammable or toxic (or both). Over the years, various refrigerants have been used in automotive air conditioning. Let’s take a look.
Early DuPont promo film demonstrating non-flammability of Freon
In the 1930s, GM and DuPont partnered to develop safer refrigerants and came up with Dichlorodifluoromethane, better known by its trade name Freon, or today known simply as R-12. Here was a refrigerant that seemed (at the time, anyway) to be completely harmless: R-12 was odorless, colorless, non-flammable, and non-toxic. Indeed, a common way to check for leaks in R-12 systems in the early days was to hold an open flame up to the system around areas with potential leaks.
This was a particularly productive time for the DuPont team: Between 1930 and 1935, this team not only discovered R-12, but also Chlorodifluoromethane (R-22) and a number of other less commonly used refrigerants and propellants (R-11, R-113, and R-114).
Now might be a good time for a quick sidebar to explain the conventions of naming refrigerants. ASHRAE (the American Society of Heating, Refrigeration, and Air-Conditioning Engineers) has long been responsible for keeping the “master list” of refrigerant identifiers, all of which start with the letter “R” (for refrigerant, of course) followed by a numerical designation. Methane-based CFC refrigerants are identified with two-digit numbers, indicating the number of hydrogen atoms (plus one) and the number of fluorine atoms, respectively. Following this convention, we can infer that R-12 is considered to be a methane-based CFC with no hydrogen atoms and two fluorine atoms, while R-22 has one hydrogen atom and two fluorine atoms.
Three-digit numbers starting with “1” (like R-113) are ethane-based, and those that start with “2” are based on propane. Numbers starting with “7” are inorganic compounds, many of which are not commonly used (or even thought of) as refrigerants: For example, pure hydrogen (H2) is R-702, ammonia (NH3) is R-717, and water (good old H2O) is called R-718 when employed as a refrigerant. Most CFCs are fully saturated (meaning that all bonds between atoms are single bonds to maximize the number of hydrogen atoms). If a CFC is unsaturated (meaning that there are one or more double-bonds between carbon or fluorine atoms), an extra “1” is prepended to the identifying number, as in the case of R-1234yf.
Lastly, there are sometimes isomeric variations of some refrigerants (isomers, as you recall from your high school chemistry, are compounds that have the same molecular formula but different arrangements of the constituent atoms). These are indicated with a trailing letter (as in the case of R-134a). You can view the full list at ASHRAE’s website, if you are interested.
Now back to automotive refrigerants:
R-12
All early automotive air conditioning systems used R-12 (with the previously noted exception of the 1953-55 Chrysler Airtemp system, which used R-22).
R-12 would go on to become the standard for automotive air conditioning for many decades, while R-22 would in turn become the standard for residential and commercial cooling applications. There are several reasons for this. R-22 has a lower boiling point, a higher heat of vaporization, and a higher specific heat than R-12, which makes it a slightly more efficient refrigerant than R-12. However, R-22 has several disadvantages that have precluded its use in automotive applications. The pressures that R-22 operates are roughly double those of R-12, which require heavier components that would, in turn, add weight and draw more engine power (recall the monster V4 R-22 compressor in the 1953 Chrysler). While size and weight are of little concern to building-installed A/C systems, these are critical parameters for vehicle applications. R-22 also has the unfortunate habit of turning corrosive when overheated or exposed to moisture, both of which are more likely to occur in a car than in a building. This corrosiveness also means that you can’t use any rubber components (like O-rings) in R-22 systems, and instead have to use more expensive flared fittings. All of these factors conspired to make R-12 the de facto standard refrigerant for automotive air conditioning, even if it is slightly less efficient.
R-134a
While early CFCs like R-12 and R-22 were at one time thought to be completely harmless, starting in the 1970s a growing body of scientific evidence demonstrated a link between some CFCs and depletion of the ozone layer. The Montreal Protocol of 1987 mandated a phaseout of the most ozone-depleting chemicals, including R-12. Auto manufacturers started switching their A/C systems over to R-134a in the early 90s, which has only a tiny fraction of the ozone depletion potential of R-12.
R-134a is not a drop-in replacement for R-12: R-134a is not compatible with the mineral oil lubricants commonly used in R-12 systems, and is also slightly less efficient than R-12 (which I’ve personally observed in systems I’ve converted over from R-12 to R-134a). For this reason, R-134a systems use different fittings than R-12 to avoid any mixup. Converting a system to R-134a may also require replacing the receiver/dryer (and possibly the compressor as well) to remove any traces of mineral oil from the R-12 system.
R-1234yf
R-134a might have been a win for the ozone layer, but it has had a negative impact on global warming: R-134a is a global warming agent over 1,000 times more potent than CO2. After years of research, R-1234yf was developed as a replacement. It has similar thermal properties to R-134a, but with far less global warming potential than R-134a (less even than that of CO2). The only downside to R-1234yf is that unlike previous CFCs, R-1234yf is slightly flammable. For this reason, retrofits of earlier systems (either R-12 or R-134a) to R-1234yf are not possible and should never be performed.
Unlike the previous R-12 phaseout, the phaseout of R-134a does not include an outright ban, in part due to the above-mentioned inability to retrofit. Auto manufacturers started switching over to R-1234yf in the early 2010s, and by 2018 (the latest year I could find data for), roughly 50% of all new cars and trucks were shipping with R-1234yf-based air conditioning systems. Some, like BMW, have switched their entire product lines over to R-1234yf, while others, like Volvo, have not yet begun the changeover and are still 100% on R-134a. Most manufacturers are somewhere in between, usually switching to R-1234yf when performing a major model refresh.
A GI donated his can of F12 to recharge my Rover SD1 a/c. Illegal at the time as UK government didn’t want drivers discharging the gas in to the atmosphere by accident. You had to go to a shop to have the system put on a recycle n recovery machine. Strange your EPA allowed risky d-i-ys?.
” Strange your EPA allowed risky d-i-ys?”
That’s a reflection of the US political system- Because the system is designed to place control in the hands of the local populace, US laws often allow individuals great freedom with regard to their personal property, but do place restrictions on local repair shops. For example, an owner can tamper with their emissions control system without much concern about fines or penalties, while a shop would face fines or lose their license if they tamper with the system.
There are also differences from state to state. In many states there are no auto technician licensing requirements, and anyone with a pulse and hand tools can work at the local dealership. Regarding the topic of this article, the EPA mandates a nationwide certification course for all techs working on AC systems, and techs face major fines if they vent refrigerant in the atmosphere.
Well charging your AC yourself existed long before the EPA.
Also it is important to note that back in the day a “boat horn” was a device you screwed on top of a can of R12.
Yeah you could use the standard can off the shelf of your auto parts store, but enterprising people did sell it as boat horn gas, of course with a premium.
https://www.ebay.com/itm/Vintage-Sparton-Air-Horn-Gas-Cartridge-Refill-Marine-Boat-R12-R-12-Freon-Chevy-/254577078313?nma=true&si=U8CMgm4MAslLnG834X6sLLxiHj0%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557
I was going to ask who else remembers “the good old days” when escaping CFCs would blast hundreds of air horns at sporting events? LoL
…shrink-fit parts by freezing.
Fight fire.
Frost up things like angry wasps’ nests into a
safe-to-remove balls of ice. LoL
And of course liberally blast off to sweep charge AC systems without a pump-down.
Yup and liquid R12 was used as cutting fluid/coolant to extend tool life and prevent hardening of the material in high production manufacturing.
Residential and commercial building HVAC had to deal with R-22 being phased out too. Ten years ago or so the condenser took a dump on my rental house in southwest Utah. With the increasing cost and decreasing availability for R-22, I elected to replace the whole system with a new R-410A system. Not cheap but cost somewhat offset by utility co. rebate.
Tom: This continues to be very informative. I await your discourse on the various types of compressor utilized. I’ve heard stories of the Chrysler ‘V’ type allegedly being capable of being used to cool buildings. 🙂
Tom may correct me, but I have understood that virtually all automotive systems could handle a decent sized building – the reason being that part of the design brief for an automotive system is to get a car interior cooled down from maybe 130 degrees down to 75 or so in a matter of minutes – something a typical building’s system will take hours to do.
I think that has more to do with the relative volume of air in a building, no? Just like it’s perhaps quicker to cool down your Fit than your Sedona on a hot day, a building is on a whole other order of magnitude. From what I recall, the spec for a house system is to cool the air down at least 14 degrees between intake and vent output, and then the air circulates back through the system several times until it’s at the desired temp. How many Cubic Feet / Minute are moved depends on the size of the fan unit and this the expense/size of the system, which obviously varies depending on the size of building and total air inside it.
A bit of Googling suggests automotive a/c units are in the range of 10-20k BTUs. That’s pretty good size. Enough for a smaller house.
Yes, Automotive A/C compressors, particularly those of yesteryear have enough capacity to cool a small building. There are a number of reasons why that is true.
JPC is on the right track in that it is intended to cool a vehicle in a matter of minutes in extreme conditions.
In a typical car the solar gain can be orders of magnitude greater than a typical building. You can’t really draw the curtains or blinds on a car, though you can use shields when parked. Not only does the sun heat up the interior and interior materials it heats up the metal of the car and that metal will conduct it into and radiate it into the interior.
Then you have that big lump of metal running at ~200 degrees and the exhaust adding heat to the firewall and floor. (at least in ICE vehicles)
Yes there is insulation and thermal breaks in the form of carpet, door panels ect but it is minimal and in fact they have thermal mass that will add heat to the air in the vehicle as their temps are lowered from the 100+ degrees they are when you start the car.
Speaking of the air in the vehicle it needs to be design to work with the system being fed outside air, except in the most extreme conditions.
Oh and it needs to be able to do that with the engine at idle, turning the compressor at far lower than optimal rpm.
A well designed, properly functioning system should be able to create 60 degree discharge temps in 100 degree weather with the fan on high and fresh air, often drawn across that hood with the ~200 degree lump of metal under it.
Meanwhile in a building application the solar gain is usually much better managed, insulation and thermal breaks are much more effective. The compressor would also be operated at the most efficient rpm, giving 100% of its capacity 100% of the time it is operating. The air is mostly recirculated and you only need to maintain the temp of the air and contents not drop it dramatically.
The limit of the car system is the size of the evaporator which is sized for the car and its extremes, but both the compressor and condenser need to be designed to provide that capacity while operating at a fraction of their ultimate capacity when the car is stopped and idling.
My ’65 and ’66 Imperial’s with Dual A/C on R-12 would cool cars in 1 min on 100 day, R134, 4-6 min, my ’63 Electra convertible 1-2 min on R-12 , the same on R-134.
I’m a bit surprised Volvo is dragging its feet, given how they cultivate an image of being environmentally progressive.
True, but only A/C nerds such as myself are likely to notice or care. 😉
I’m of the understanding that it’s market specific and Volvo do in fact use 1234yf in some places.
https://www.volvocars.com/en-ca/support/manuals/xc40/2019w46/specifications/specifications-for-fluids-and-lubricants/air-conditioning-specifications
https://www.volvocars.com/uk/support/manuals/v90/2018w17/specifications/specifications-for-fluids-and-lubricants/air-conditioning—-specifications
Mercedes in particular was extremely concerned about R1234yf about a decade ago due to its flammability. I believe they have developed some sort of proprietary CO2 based system that they have approval to use instead.
Yeah I think Volvo is one of a number of companies that has an issue with both the saftey and cost of the new stuff. There were a number of lawsuits about requiring the use of a patented chemical.
Didn’t know about 1234yf’s flammability, good to know! My understanding is that it is really expensive compared to 134a, does anyone have particulars on that?
R-1234yf is about $40 for an 8 oz. can.
Yep it’s expensive. I gather mostly due to Honeywell owning the patent until 2025. Honey well has been pretty aggressive at going after copycats so I’m sure the pricing is 90% to do with the patent rather then actual cost to make.
Excellent post, Tom!
I was wondering that since R1234yf won’t retrofit to R134a systems, what’s different in the design for R1234yf systems?
“what’s different in the design for R1234yf systems?”
The compressor, condenser and evaporator are basically the same, but the lines and connections are designed and routed in a way designed to reduce or eliminate any exposure to heat sources on the vehicle. Manufacturers have been doing this with fuel lines for many years now, so they already had policies ad procedures in place to guide them in this change.
Thanks, Dave! 🙂
In addition to what Dave said, another component of an R1234yf system that so far hasn’t been common on older systems is a new heat exchanger built into the lines. If you look at the lines coming from the firewall on an older system, there are two independent lines (larger diameter low pressure suction and smaller diameter high pressure liquid line). On the new 1234 systems, this line is merged into a single piece. The high pressure liquid line routes through the inside of the suction line, which allows some heat to bleed off into the low pressure, low temperature line. This is, if I’m not mistaken, supposed to make up for some of the efficiency losses of the newer gas/system design. These systems also run with a smaller quantity of gas (approx 1.1 lb on average compared to 1.5-3lbs on 134a) and do not include a receiver/drier/accumulator. Not sure why the latter is being phased out, but has been slowly disappearing since about 2008 from what I’ve seen.
In the changeover years when remaining supplies of the no-longer-produced R-12 were being sold off at ever increasing prices, the only way one could buy it legally in the USA was to become certified in refrigerant recovery practices. This was easier than it sounds. There were webpages with the training materials and a thirty-question test. Pay the fee, which I recall as $25 or so, and you could then print out your certificate. As I had several R-12 cars and over a dozen cans of R-12 in the stash, I figured on holding off until I ran out and needed more. That never happened. One by one, the R-12 cars departed the “fleet” until there was one left, a 1992 Mercury Sable…the year before Ford changed them over to R-134a…and it had one of those pesky Ford A/C spring-fitting leaks. I decided it was time. I took the car to a shop which recovered the remaining R-12 (probably over a pound of it) and oil and kept it as his “fee.” Replacing the O-rings with R-134a-compatible wasn’t difficult, and they are actually a tiny bit larger and seal better. Vacuuming the system and installing the R-134a were a snap, and the system performed adequately, with very little degradation afterwards. That did it. No more R-12 cars. I gave away a few cans and still have a 30-lb. flask. My brother has a mid-1980s Mercedes 300SD which, last I heard, had nonworking air conditioning, but he’ll have to drive it here, 500 miles, if the cause is no refrigerant.
I’ve heard (can anyone verify?) that because there are so few R-12 vehicles left, and a lot of R-12 has been recovered from scrapped and converted vehicles, that R-12 prices have gone back down.
It’s still good to use R-12 in old cars originally equipped with it, if you can. Especially if the compressor is mounted near the highest point in the system as it often is in older cars. I’ve been told that in a R-134 system the oil is more likely to settle out and go to the low point in the system. I grenaded two compressors trying to run a ’74 Cadillac on R-134. Many newer cars have the compressor mounted down low.
There’s an A/C shop near me that has been around forever and still works with R-12. Definitely a blessing for us old car guys.
Yes when I got into the AC game a 30lb tank of R12 was expensive at ~$300 and it eventually went to ~$1200 before settling back down to ~$500 the last time I purchased it.
That would be my Mustang, Park Lane, and Polara which are all mounted high. I do have a store of R-12 but then I never really drive those cars when I would need to use AC. The 91 626 has a low compressor but uses R-12. However, the compressor is shot and I have a new NOS compressor, drier, hoses, and condenser to install. Question is do I use R-12 I have or the R-134 I have?
A NOS drier could have the R12 only desiccant, not the stuff designed for R123a and R12.
1992 Fords came with R134a compatible o-rings and hoses. The only thing that you were supposed to change was the receiver drier.
ALSO…during that time there were products claimed to be low cost drop-in replacements for R-12. Their thermal characteristics were close but they were based on mixtures of flammable gases…propane and the like. Venting a couple of pounds of propane in a collision that ruptured the A/C condenser could be entertaining. No, thanks!
Propane and propane based products are popular with farmers and heavy equipment guys with Air conditioned cabs. It’s cheap and easy to work with and I gather works well as long as you don’t have a leak.
In a sense the “farmer” charging from a barbecue tank may be better off than with a fill of R290 real (propane) refrigerant. Purity issues aside, at least the barbecue propane contains odorant, 290 is odorless.
Seems strange -make that crazy- to promote filling leak-prone systems with essentially the same flammable gas in an odorless form.
Lots of useful information, and fine explaining/teaching—a pleasure to read today. Now I’m gonna have to figure out what’s in my 2018 Ford…..
Most cars should have a label under the hood stating the type of refrigerant in the system to prevent possible cross contamination.
ALL motor vehicles sold in the US, in the last few decades, have the refrigerant type and quantity on a sticker under the hood when it leaves the factory. Of course over time those stickers can go missing, particularly when the vehicle is in a crash and the repair facility fails to obtain and install the proper sticker on the part that was replaced.
Wow, the R1234yf thing is new to me as both of my daily drivers are 10 and 16 years old. Very informative. When I install new components in my 67 LeSabre with factory air conditioning, I think R12 is the way to go. Any thoughts? I was in the thick of the refrigerant drama back in 1989-1992, abet on the commercial chiller side with Carrier Building Systems and Services as a sales engineer. R-11 was out and and R-123 was and absorbers were coming back. All low pressure. R134a was a big deal but a hard sell as it was high pressure, variable vans compressors were loud. Very confusing time.
Going prices for a can of R-12 here in No. California is $20 on Craigslist.
I believe California slaps a $10 tax on cans of refrigerant.
I managed to get through my son’s years with his 89 Grand Marquis with still a can or two of R-12 in the basement.
I recall an early loophole in the regulation of R-12 sales – the small cans typically purchased by consumers got outlawed (going from memory) but not long after I went into an auto parts store where they had a big display of the 30 lb cans priced at about $100. I thought about buying one but decided not to. It probably worked out OK.
Is anyone taking bets yet on what the weakness is in R1234yf that will eventually get it outlawed? Nobody probably knows it yet, but you can bet we’ll find out some day.
My bet is that in 20 years, R-1234yf will be found to cause nut allergies, and will be banned. Let’s check back in 2040 to see for sure.
Oh, I’m allergic to nuts – mainly those who believe science is a plot – so I hope they’re banned before then!
Actually, I reckon we’d have banned the car itself in 1888 if we knew of the billions of deaths and untold suffering from the machines, the pollution and the wars it was to be responsible for.
That said, this development DOES have a ring to it of “There was an old lady who swallowed a fly”” about it.
Thank you for communicating this information. I always enjoy your articles about automotive air conditioning systems, and this explanation complements them nicely.
Auto applications employing R-134a and R-1234yf (non-chlorinated refrigerants) require PAG oil for a reason. A refrigerant/oil mixture when discharged from an operating compressor is hot and flows freely.
The problem resides in the cold evaporator coil and suction line. The oil just wants to sit there. Insufficient oil return = scrambled compressor.
In an R-12 (or any other chlorine base refrigerant) system the chlorine component of the refrigerant carries the mineral oil back to the compressor. The newer refrigerants have no chlorine molecules for the mineral oil to attach. Hence the change to PAG oils which don’t need a chlorine molecule for oil return to the compressor.
Compressor elevation has no bearing on oil return in a properly designed system with the correct refrigerant/oil combination.
I would like to point out that the above video is somewhat misleading. Refrigerant displaces oxygen causing the flames in the video to extinguish.
R-12 has an A1 safety rating meaning it will not sustain a flame on the withdrawal of an ignition source. Hence the “non-flammable” safety rating. However, when exposed to a source of sufficient flame or high enough heat R-12 produces phosgene (nerve gas). Extremely toxic. Old time refrigerant detectors used a heated (normally by a propane torch) detector plate set up which would indicate the presence of refrigerant by changing the color. Mechanics were advised to use in a well ventilated space.
I could go on and on about refrigerants but I’ll stop.
I spent 25 years in the commercial refrigeration industry in field sales for a wholesale distributor whose product offering included DuPont refrigerants. The time of the refrigerant changeover in the OEM/Aftermarket from CFCs to HCFC/HFC refrigerants was quite interesting and challenging.
Some large scale commercial refrigeration systems still use ammonia, for example grocery distribution centers. You can tell if you see a windsock on the building, so emergency personnel can tell where the (rather toxic) cloud is drifting during an accidental leak.
I assume it’s for cost reasons – or is it more efficient too?
Ammonia is a natural, efficient, cheap refrigerant with a wide temperature range. Anything above 16% has the potential to explode. Large/catastrophic leaks can be diluted with water. It is corrosive and and is piped in carbon steel.
Carbon dioxide (R744) is now making inroads as a refrigerant.
R744 makes me nervous, but who knows, could be the wave of the future. Based on what I’ve read so far, the most significant limitations to a CO2 based refrigerant are operating pressures and safety. CO2 systems require substantially higher operating pressures relative to existing refrigerants (R134a discharge pressure ~200-300psi; R744 discharge pressure >600psi), which also requires heavier, more durable components (i.e.: more weight, higher costs). In addition using CO2 as a refrigerant requires the use of a secondary cooling/heating loop in order to avoid venting unbreathable CO2 gases into the passenger compartment. Think stationary chillers used to cool a building – refrigerant gases cool a separate medium (water, or other liquid) that is then circulated through pipes and heat exchangers throughout the target zone.
Safety issues notwithstanding, R744 does appear to have a lot of potential in heat pump applications due to these higher pressures (and subsequently, temperatures).
No doubt technological advancements will either address, or improve upon these issues in the future though.
Tom, you have a great way of explaining things — thanks for this overview. I’ve often wondered about some of these details, but have never explored it until now.
A side kick of R12 was Halon 1211 als called BCF and Halon 1301, these were the very best fire fighting means ever, but banned by the 1987 Montreal protocol for ozone depletion gases.
Today it is stiil used as a fire fighting medium for jet engines and onboard submarines, the reason it is used onboard of submarines is that Halon does not suffocate people while Co2 does and you need very little Halon to extinguish a fire.
To pull it auto motive, remember the eighties Formule 1, when while racing Turbo engines would catch fire and woooosh like magic the fire would go out ?
That was done by a small Halon cylinder with a pull wire to activate it by the driver!
Halon was very efficient because you needed very little to put out a fire.
Till this day there is no extinguishing medium that has been able to replace Halon, not FM 200 nor NOVEC.
Great stuff as it always is from you, Mr H.
I had absolutely no idea of this refrigerant change. Quite wry that the replacement of an agent thinning the ozone layer should turn out to be a dastardly agent for global warming.
A bit sad to contemplate, too. With the ozone damage issue, there was global scientific consensus in the field, co-ordinated international action strongly supported by the US, and the problem was addressed. With anthropogenic global warming, it came close to being the same, but lobbying and politics intervened, and, well, here we are (or not, with Australia gallingly one the worst laggards too).
Could an R134a system be converted to R-1234? That is, is it scientifically possible and cost-prohibitive, or simply not possible?
1. When the patents run out, the refrigerant becomes a “political issue” and “must” be banned, so that something with fresh patents and higher profits can take it’s place.
2. In “the good old days”, an automotive A/C system could be fine-tuned to produce air temps that were “just” warm enough to keep the evaporator from freezing. The dash vents would blow tiny ice crystals–miniature snow. Today, dash-vent temps are ten–twenty degrees warmer. Another reason cars have tiny, tinted windows–less heat load from sun, ’cause the A/C is designed to be pathetic.
3. Sometime in the mid-70s, GM switched A/C systems from the sort that got genuinely cold, to a “more efficient” “higher fuel economy” system that shut off the compressor to “save energy”. The new system was called “CCOT”, Cycling Clutch Orifice Tube. Instead of deliberately running the A/C compressor all the time, and regulating evaporator temperature with an expensive variable orifice that could be tuned to keep the evap just above freezing under most conditions, they went to a dead-simple, fixed-size orifice and ran the compressor “as needed”. GM Marketing pretended this was for “fuel economy” and a benefit to the consumer, but in practice the compressor ran all the time anyway (unless the refrigerant level got low due to system leaks). They merely reduced the cooling power of the A/C, and tremendously cheapened and simplified the control mechanism so as to build-in additional profits. The system wouldn’t flow enough refrigerant into the evap to freeze it most of the time, but if it got even close…the compressor shut down. It saved a lot of money for GM, but the days of powerful A/C were d-o-n-e. Since then, CCOT has given way to other mechanisms including variable-displacement compressors. A side-effect of the CCOT system was that, given the lazy, no-power engines of the time, a vehicle on cruise control at highway speed would drop 2–3 mph every time the compressor engaged. Then the cruise would yank the throttle open, struggling to recover speed. The cycling compressor was usually a sign that the system was low on refrigerant.
4. I remember when a “pounder” (“16-oz” including the steel can, but over time the net weight went down due to manufacturer greed) can of R-12 was less than a dollar. My supervisor showed me how to chill automatic choke coils by blowing R-12 on them. I bought a compressed-air choke tool to cool them with, instead. (No, it didn’t work as good.)
5. I bought an expensive (at that time) electronic R-12 leak detector, because it seemed to me to be completely CRAZY to use the “shop tool”, an open-flame leak detector of the sort described by Phil in another post. Phosgene is something best not played-with.
Oh, brother.
1. I was wondering when that patent-expiry hooey would show up in this discussion thread. It wasn’t true about R12, and it isn’t true about R134a. Storytime can be fun, and chasing conspiracy theories appears to have replaced baseball as America’s national pastime these days, but maybe just here on this site could we stick to facts and save the fairtytales for bedtimes and the ghost stories for campfires?
2. Ton for ton, today’s auto A/C systems in proper repair generally do a better job than yesterday’s. Not only because the state of the art and science of HVAC engineering and construction was a whole lot less advanced in the imaginary “good ol’ days”, but also because we have much better insulation, we have high-R/low-E glass, and other ancillary factors. A person whose knowledge is overshadowed by his beliefs can louse up the performance of an A/C system of any age, in any kind of car, then blame it on expired patents, the EPA, the FDA (while we’re at it), and any number of other parties.
3. Compressor clutch disengagement to avoid evaporator freezing did not start in the 1970s. It is one of several strategies employed for many years; others include various methods of suction throttling, etc. Compressor cutout on hard acceleration goes back a very long time, too; it was a feature of A/C systems on police cars and other heavy-duty vehicles for quite awhile. When the gas crisis hit, there were aftermarket kits available to cut out the compressor under hard acceleration. Automakers employed this strategy during the era of low-powered engines, correctly reasoning that maximum possible acceleration, when called for, was likely more important than minimum possible cabin temperature.
Full-time compressor operation with evaporator pressure/temp regulation by dint of suction throttling or variable compressor displacement is also much older than the ’70s. Such a strategy was used in an enormous number of Chrysler Corp systems dating back at least to the early 1960s, for just one example.
GM’s fixed-orifice CCOT probably did overly prioritise cheap cost at the expense of system performance, but that doesn’t mean newer A/C systems are poopy and old ones are awesome—not by a long shot. Anyhow, there are aftermarket upgrades to bring a CCOT system up to the performance levels of a TXV system.
4. Yeah, Freon used to be cheap. And a dozen eggs, a pack o’ smokes, a loaf o’ bread, or a gallon o’ gas (good old-fashioned he-man Ethyl, not wimpy ol’ stupid ol’ weenie ol’ unleaded!) used to cost 29¢. We don’t live in 1964.
That was one hell of an explanation. Thank you!
I worked on lots of CCOT systems and they worked. The only truck that the CCOT system didn’t work so good in was the Brigadier. It didn’t cool as well as the Astros and Generals. The odd thing was before the CCOT system came to the heavy trucks GM used three different systems, Astro’s, General’s and Brigadier’s had different types of throttling for controlling the flow of R-12 to the evaporator.
I had a Chevette, 1980 1.6L with a 3speed auto. It cooled fine but it did kill the fuel mileage. I did an experiment on a summer cruise on I-80 across Nebraska. 31 mpg with air off, 24 mpg with it on.
The cooler the outside temp the more the clutch cycled. Once in got hot enough it would not cycle.
I also had an engine breakdown that I blamed on the A/C cycling clutch system.
The crank V-belt pulley flew off one day when my wife was driving it. She looked in the rear view mirror to see pieces bouncing down the road behind the car.
A single bolt in the center of the crankshaft snout held the pulley on and the camshaft belt drive sprocket was sandwiched in behind the pulley. The sprocket flew off with the pulley and that was it for the engine running. There is two little nubs on the sprocket that indexed with two little holes in the pulley to keep the pulley from shifting. The pulley also had the timing marks on it. My theory was the cycling of the A/C clutch caused the pulley to shift back and forth, loosening things up a bit and now it could work on the bolt itself until the bolt fatigued enough to give up and break. GM’s fix was a new bolt and a very large and extra thick washer under the bolt to hold that pulley in place. Got it fixed under warranty, even threw in a new crankshaft. The dealer screwed up the repair which is another story.