Rejuvenating your vintage air conditioning can be a cool project | Hagerty Media

[Hagerty]

With the start of summer around the corner, a gearhead's fancy turns to thoughts of... air conditioning-so you're not sweating like a pig in your favorite vintage car. OK, maybe that's just me.
https://www.hagerty.com/media/opinion/the-hack-mechanic/rejuvenating-your-vintage-air-conditioning-c...

[MATTMERICA]

I've been wondering about vintage air for a bit now, what great timing! I have a 1979 dodge power wagon - a macho wagon actually - that would be great if ti had AC, now I can start looking in earnest. THANK YOU

[tonyjustin]

My advice is to pass on Vintage Air. Poor customer service and the heater coil is tiny/ineffective. I installed Vintage Air in a '72 Nova and could not drive it if the ambient temperature went below 20 degrees. The A/C worked fine but the heater part was useless. The poor customer service came from when they shorted me parts (firewall grommets) and also sent the wrong evaporator hose and I had to pay for their screw-up. I bought the entire system from a Vintage Air booth at the Nashville Good Guys show a few years back so there is no blaming anyone other than Vintage Air. I installed Classic Auto Air in my '72 Mustang fastback and it is great - hot or cold.

[Doug42]

I can’t understand why a company would quibble with a paying customer over two rubber grommets and an incorrect evaporator hose. Now thousands of potential customers are reading about poor customer service. Up to today I was told Vintage Air was a good system.

[Smithsonite]

I've had great luck with ACKits.net ( https://ackits.net/aftermarket-ac-systems/ ) as far as customer service goes. I bought alot of components there for my '86 Grand Marquis and '93 Volvo 940 A/C systems overhauls.

They sent the wrong accumulator for the 940. Funny thing, it actually held pressure for a WEEK without ever sealing properly! That's a testament to Nylog on o-rings right there. Anyway, they told me to keep the wrong one and refunded my money right then, since they couldn't find a correct replacement. I had a hard time finding the correct one until I got on a Euro parts website.

[mbr2000]

Thanks for your comments. I've had pretty good service from V/A in the past, and my local dealer is great. However, Old Air is 35 miles from my house, and I like their blower/evap unit a little better. I'll have to pay them a visit.

[OHCOddball]

IF you have all the original parts that are in good shape, it IS possible to change the refrigerant but realize that 134a and R-12 have different pressures and temperatures that they like to run at and for most efficiency, the evaporator and condenser sizes are different as the article said. Plus, the hoses have to be changed as the ones for 134a have a lining in them. They will eventually leak if you don't. If you don't have a complete system, buy a complete aftermarket set-up. It will still be a compromise as they are one size fits most.

[Air_and_Water]

I have heard of people using a Prius compressor (and I'm sure there are others like it) as it's electrically driven, so the compressor can be mounted anywhere as long as it gets a good supply of electricity. That piques my interest, as it solves several problems with putting A/C in a car with a tight engine compartment. Has anyone here done that or know of a web site where that's been shown as a how-to?

[MBardenwerper]

I am so glad this issue is being covered. Good article, but there are a few things I would like to offer. First, when refurbishing an old system, flushing is not needed unless the original system was damaged by a compressor blowout. This can be confirmed by inspecting the orifice or control valve and looking for foreign matter, which is likely from bits of the trashed compressor. In this case, all components must be flushed and blown out with compressed air. Second, flare fittings are fine, but the hoses must be replaced. To do this, fittings with matching configuration can be sourced (angle, size and gender) that are designed for use on R134a compatible hose. You also must replace your clamps with ones designed for R134a. The original clamps, which look like those used on radiators, are not strong enough to seal. You used to have no choice but to go with crimped ends, which required expertise and tools beyond the reach of DIYer's, but now there are systems that use bands attached with inexpensive hand tools. The other issue I would like to address is the retrofitting of R134a into existing systems. You must remove all R12 from the system, but the R12 oil is not an issue if you do not use PAG, but instead use ester oil. I still recommend replacing the receiver-dryer, because this does remove most of the old oil and you get a fresh start with the all-important dryer dessicant.

[MBardenwerper]

I would also say that when adding the ester oil, only use enough to replace what is normally lost in a component replacement. For instance, receiver-dryers retain some oil so only add what is needed for that component.

[thehackmechanic]

I'm posting the same response to several people about refrigerants, oils, and flushing.

When I rejuvenate a system, it's because it's a) old and b) long dead, in which case the only component I reuse is the evaporator assembly. I always (well, almost always) like to start with a known-clean system, and that means removing the evaporator assembly, taking out the expansion valve, and flushing the evaporator core. My perspective is: Why would I want to leave a question about the cleanliness of the only component that I'm reusing?

If, on the other hand, you're converting a system without replacing the compressor, condenser, and hoses, I can appreciate how the perspective is different. If your experience is that you don't need to flush the entire system before converting unless you see contamination, and you've had good results, I can't contradict you.

Put another way, you're correct that I don't know for a fact that removing all traces of the R12-specific mineral oil is absolutely essential. My routine of flushing has more to do with being absolutely certain that I'm starting with a known-clean system.

[GaryB65]

Another useful article from Rob. I have a minor quibble about the air conditioning theory discussion, and a request for more discussion on rejuvenating an existing R12 system.

The paragraph on theory talks about cooling from expansion of the gas, and the condenser cooling the gas. What really drives the heat transfer in the system is the phase change from liquid to gas across the expansion valve, and the phase change from compressed gas to liquid across the condenser. The BTUs transferred from the latent heat involved in the phase changes from evaporation and condensation of the refrigerant is much greater than what is involved from the simple expansion or compression of the gas while in that phase. The figure in the article portrays that, but the brief description in the text does not address the importance of the phase changes.

My request for more info is the case where original system worked fine up to the point where the old A6 compressor locked up. The system is still closed and after 20+ years still shows a slightly positive pressure on a gauge set. I would like to hear Rob's recommendation about what steps to take to rejuvenate this system, beyond a rebuilt compressor, new hoses and receiver/dryer.

One final note - I would not recommend ester oils for R134a system. I work for an engineering company and we road tested R134a/ester oil systems for a European car company in the late 1980s. Of three cars tested in central Texas heat for 10,000 miles each, one of the three suffered a complete compressor failure. The manufacturer went back to PAG oil after that.

[thehackmechanic]

If the compressor locked up, there's the possibility that it shed metal or other particulate matter such as shredded seals into the system. I'd strongly recommend that the entire system be flushed out. At a minimum, when you disconnect the hoses from the compressor, examine them for contamination. If they look clean, you could take your chances, but if you see goo or particulate matter, it may well have found its way into the evaporator and expansion valve. I always (well, almost always) disassemble and flush systems to be certain. What else you do depends on the car and your level of expectation. If the rest of the system is tight as verified by pressure-testing, and you were happy with its performance with R12, you can save yourself a lot of work by recharging it with R12 and not upgrading anything, but as I said, as time goes by, I'm less and less sanguine about it.

[GaryB65]

Thanks for the reply, Rob. I have a friend who is a former Corvette tech (late 50s to 66) that I hope to have help me in rejuvenating the AC in my 71 Convertible. He is 80 now so we'll see how that goes. I will check all of these items you mentioned. My biggest concern is taking apart and removing 50-yr-old items to properly flush them.

You and I have a few things in common - we are both engineers (I am Chemical) and we both have lived in Austin, TX.

[GaryB65]

Just a couple of follow-ups to my initial comments, if anyone comes back and treads this ground later. I ended up buying Rob's book and the book properly describes the role of the heat of vaporization and condensation of the refrigerant on heat transfer in the AC system. Apparently that detail got left out of the "Cliff's Notes" in this article for the sake of brevity.

Also, I'd like to soften my earlier comment about ester oils. These are each synthetic, custom-designed ester molecules, and the state of development of these lubricants has no doubt advanced in the 32 years since my bad experience with one specific formulation, so don't take my comment as condemnation of ester oils as a viable selection.

[margozp]

Great read, very cool 😉

My brother and I went through both of our Pontiac's AC systems recently. We switched from R12 to 134a with no problems. We sourced all parts from OldAir Products https://www.oldairproducts.com/ Fantastic guys at the shop, very helpful with advise and gave us a great deal on all of the parts we needed.

We decided to dump the Harrison A6 compressor and go with a modern compressor (pro6Ten) that fits in the same OEM mounting brackets... also opted to replace the compressor muffler with an oem one that fits the modern compressor. In addition we replaced the POA valve, expansion valve, dryer/receiver (that's a must) and the hoses. We flushed and leak tested the condenser and evaporator... they passed the test so we reused them. We did reuse our hose connections by sending our old hoses and connectors intact to the hose company. They cleaned the connectors up and fit the new hoses for 134a. We did this because the replacement connectors out their did not seem to be the same shape.

One thing I would recommend for Pontiac's anyway...use a temp switch instead of a pressure switch to cycle the compressor... we saw that the pump was constantly turning on and off ( every few seconds) that the correct pressure could never build up. Using a temp switch on the POA valve gave the system the hysteresis it needed to perform properly.

We had to have a shop evacuate the system and recharge since we did not have a good enough vacuum pump.. but we installed everything our selves and the result was two awesome AC systems blowing crazy cold air!

[DrOverboost]

I discovered another issue with resurrection of old a/c systems. The new 6.3 liter roots supercharged engine in my 1980 Corvette revs to 8000 rpm. Compressors disintegrate around 7000 rpm. Solution: MSD makes a rev limiter switch which can be set to go on and off at 2 designated rpm’s. It turns on at 1500 rpm (so my idle doesn’t suffer) and off at 4500 rpm. If I’m going faster than that I want the extra horsepower at the wheels anyway. If I’m in a traffic jam I just rest my foot on the accelerator pedal to keep the rpm’s over 1500.

[CharlieB3]

Thank you for sharing your wonderful knowledge with us. I am on the extreme low end of tech and mechanical stuff but deeply in love with cars of the '50-70's and understand vintage air conversions have probably saved many cars. What I do not understand is how talented owners can go thru the expense of these wonderful installations yet hardly any ever buy a dash from a scrap/recycle facility than includes factory a/c outlets and ductwork. I don't care for most vintage units that look like a big black plastic box with chrome knobs. Is it that hard to do after all the mechanical stuff?

[thehackmechanic]

How you react to the look and feel of an aftermarket evaporator assembly under your dashboard is a personal thing. The hot rod world is all about rolling your own, so there it's usually not a big deal, but with other vintage cars, it can look out of place. Unfortunately, depending on the car, sourcing everything for an original interior a/c installation including dashboard with integrated vents, evaporator assembly, and console may be prohibitively expensive or simply impossible due to supply and demand. In addition, people are sometimes swayed by the possibility that the blower fans in old evaporator assemblies may be weak, whereas those in newer units may blow stronger and move more cold air into the passenger compartment. It really depends enormously on the individual model of car.

[farna]

The system in my car is a hodge-podge of old and new. Original to the car evaporator and expansion valve/temp switch, parallel flow condensor from a salvage yard (90s Chrysler LH platform), Sanden compressor (originally 88 Jeep Comanche -- where the 4.0L came from, since replaced with new aftermarket part), and universal dryer. Works great charged with R-134A. I've been thinking about replacing the temp unit and expansion valve since the temp control is a bit "loose" and it may perform better with R-134A with an R-134A specific expansion valve. The only issue I'd have is that the custom made barrier hoses have flare fittings for the old evaporator and o-ring for the newer condensor and compressor. I've run ES-12 in it, but last time I had it charged (had to discharge to replace engine) I had it done professionally with R-134A. ES-12 worked great, just couldn't get it recharged with that at the time I wanted to drive the car.

[hyperv6]

My 85 Pontiac still has the original R12 from the factory. I never seen a system last so long. I already have R12 to go back in if the seal leaks.

The R12 gets to nearly 40 degrees at the vent. It is just a better product.

I also work for a  intake Air Dealer. I can say they are a top notch mfg and product.  I work directly with them to set up AC units and they have been great. Yes once in a while there are issues as most systems are custom and I never had an issue unresolved. 

I have to get these right as I sell these globally and can not afford issues in Perth, Tokyo or in the Middle East. 

Often service is best working with a retailer as that is their job retail. Dealing direct with mfgs can vary as they are not retailers. If you don’t know who to call it can be challenging. 

[DougL]

Rob, I am curious about your statement that "all traces of the old R12-specific mineral oil must be flushed out before the R134a-specific PAG oil is introduced". This certainly is different than what I was taught as a GM mechanic, and different than my personal experience. GM said the oils did not mix and the R12 oil could remain in the system, but it was necessary to add the recommended amount of PAG oil. I have converted a number of systems to R-134a this way, just adding PAG oil and changing refrigerant type and service fittings. The results were pretty good although in some cases there was a noticeable reduction in cooling. I never did have a compressor failure from not flushing out the old oil.

[thehackmechanic]

DougL, I'm posting the same response to several people about refrigerants, oils, and flushing.

When I rejuvenate a system, it's because it's a) old and b) long dead, in which case the only component I reuse is the evaporator assembly. I always (well, almost always) like to start with a known-clean system, and that means removing the evaporator assembly, taking out the expansion valve, and flushing the evaporator core. My perspective is: Why would I want to leave a question about the cleanliness of the only component that I'm reusing?

If, on the other hand, you're converting a system without replacing the compressor, condenser, and hoses, I can appreciate how the perspective is different. If your experience is that you don't need to flush the entire system before converting unless you see contamination, and you've had good results, I can't contradict you.

Put another way, you're correct that I don't know for a fact that removing all traces of the R12-specific mineral oil is absolutely essential. My routine of flushing has more to do with being absolutely certain that I'm starting with a known-clean system.

[61Rampy]

Keep in mind that the old mineral oil (used with R12), if not mostly removed, will take up to around 8 ounces of space that should be filled with refrigerant, which could result in poor cooling. The old systems that held around 3 lbs of refrigerant may not notice, but smaller systems may pose problems. Nothing to do with oil, but something not mentioned was the possibility of underdriving the compressor. If possible, you want the largest clutch pulley and the smallest drive pulley. Draws way less power from the engine, at the expense of poorer low speed cooling.

[stevecobb45]

I couldn't help but notice there was no mention of possibly needing to upgrade the radiator for a new instillation. A/C cars usually have a heavy duty radiator because, with the extra heat from the condenser plus its extra air flow restriction, it taxes the cooling system more than normal. Most cars cooling systems are designed to just get by as far as cooling. You could compare it to towing a car & trailer & how much extra heat that would generate. Just something to think about & better to do it before the condenser install then later.

[thehackmechanic]

Yes. I'd add that upgrading to a heavier-duty radiator is almost always a good idea even if you're NOT retrofitting a/c. I'd also add that, when you install a big honking fan that draws 15 amps on a big honking condenser, you may need to upgrade the alternator.

[oldbeb]

A good article, BUT the old "R134a doesn't cool as well" comment isn't true IF the system is built correct. The main issue with R134a not cooling as well IS the condenser. As mentioned you need a parallel style condenser with fans. R134 is reluctant to GIVE UP heat, but it absorbs heat better than R12 at the evaporator!! Use the proper condenser with fans and the same size evaporator will cools as well, or better, vs. R12. The other issue is R134a pressure is greater at higher temperatures vs. R12. Again a good condenser with fans solves this issue IF you don't overcharge the system. I've had good luck AFTER I did a considerable amount of reading. The biggest problem I find with folks I help is that they overcharge the system. The easiest way to prevent this is to charge to about 75% of the estimated charge, THEN with the evaporator fan on HIGH and a thermometer in the vent closest to the evaporator core SLOWLY add R134a until the evaporator outlet air temperature STOPS dropping. Your done! If you overcharge the system it may not cool as well and the high side pressure can rise to the point of stressing the compressor. Overcharging was NOT an issue with R12 and in fact technicians tended to over charge as old R12 systems often leaked. Old habits are hard to break.

As for Vintage Air. I knew a fellow who installed their kits and stopped due to "issues".

BTW If you don't want to use bead lock fittings (cheap bead lock tools often result in leaks) take a look at the EATON EZ Clip system. Made for custom installations - so you fit the hose, cut, install fittings using a tool no bigger than regular pliers. The Hose Warehouse in Ohio carries all the Eaton fittings and hose. Eaton sells a 90 in hose fitting for tight bends! The oldest install I know of is six year old and has NEVER leaked.

[Johnr_Roberts]

Sorry, I had my '78 Cleveland Ford V8 converted when the air conditioning place 'ran out' of R12. Condenser and piston compressor cleaned, new high-pressure hoses and electric fans fitted (as well keeping as the regular fan), new heater tap. Hundreds and hundreds of dollars later - first really hot day (110+), it took forever to get cool and then cooling was pathetic compared to R12. Have rolled my windows down since for 25 years.

Had better success with converting a '91 4-cyl Camry (I had the fans rewired to run at full speed in parallel with the air conditioning running, as opposed to half-speed in series with R12). Whether it was the smaller, more efficient R12 compressor (I really like the Econ setting on this for mild days) and the aluminium condenser I don't know, BUT STILL on a 110-degree day R134a takes a looong time to get not as cold as R12, but tolerably cool.

[TG]

I have many-a-time dumped the oil out of an R12 compressor, refilled it with the appropriate R134a oil, swapped fittings and charged R134a with no additional work. I have never seen it pose a problem. Obviously I wouldn't recommend this on your numbers-matching shelby mustang, but on your moderate value daily driver collectable you will likely get away with it. Even if you don't, you will simply wind up doing the work that a full 134a conversion would have required anyway

[thehackmechanic]

TG, I'm posting the same response to several people about refrigerants, oils, and flushing.

When I rejuvenate a system, it's because it's a) old and b) long dead, in which case the only component I reuse is the evaporator assembly. I always (well, almost always) like to start with a known-clean system, and that means removing the evaporator assembly, taking out the expansion valve, and flushing the evaporator core. My perspective is: Why would I want to leave a question about the cleanliness of the only component that I'm reusing?

If, on the other hand, you're converting a system without replacing the compressor, condenser, and hoses, I can appreciate how the perspective is different. If your experience is that you don't need to flush the entire system before converting unless you see contamination, and you've had good results, I can't contradict you.

Put another way, you're correct that I don't know for a fact that removing all traces of the R12-specific mineral oil is absolutely essential. My routine of flushing has more to do with being absolutely certain that I'm starting with a known-clean system.

[Sledogpilot]

So how do you determine how much refrigerant (& oil) to use on a custom system?

[thehackmechanic]

That's a very good question. Sanden has a recipe that's difficult to follow, as it involves draining and refilling the compressor. I just look up what the original oil capacity was of the system, and if I'm increasing the size via a substantially larger compressor, add an extra ounce. Your mileage, as they say, may vary.

https://www.buyautoparts.com/blog/sanden-ac-compressor-service-operations-oil-change/

[Filou96]

Hi , Thank you very interesting !
I live in France and restore a Mustang 65 FB, I use Classic auto air products
I will use Duracool 12a instead of R134 , it has many advantages for DIY
You can make pressure test with Argon too ( if you have a TIG you have Argon ) , so you dont have to buy a nitrogen bottle.
Regards from France

[rgelner]

Nice article, i would like to share some information. I am in air conditioning and there is and always has been a drop in replacement made especially for refrigerant 12. It is 416A, readily available from many sources such as ebay. It is a drop in, you can top off or recharge the system, mixes well also. I have been using it for years in different applications, refrigeration and automobiles. I never understood why people went crazy paying high prices and getting in trouble for importing illegal 12 when there is a direct replacement. The public was never informed. Anyway guys it is out there, save your money and no need to convert to a different refrigerant.

[ppointer]

Your articles are the best! Who else can make automobile AC an interesting topic?

[omac]

I rejuvenated the a/c in my 1972 Lincoln Mark IV. Everything was there and intact but no freon. Replaced the drier receiver and compressor. Installed new O rings and took it to a shop with an a/c machine. The a/c with auto climate works great. Everything works as it should and is very cold. Glad to see others are doing the same thing.

[Flashman]

Check the caption on the fourth picture.

[Maestro1]

Thank you Rob. I have a Cadillac that is early 90s and will need various levels of surgery including its a/c. I won't do it myself but I am lucky to have an ASE guy about 18 miles from here who does excellent A/C work. Hagerties don't worry; I bought it for practically nothing. Which is what it's worth in its current state. But it's all there, suffering from neglect.
Everybody stay well.

[Smithsonite]

Great article. Just one correction: The statement, "a car never “just needs a recharge” isn't true. With vintage cars it is ... sort of. I say sort-of since most sit idle, which allows refrigerant to seep past the shaft seal on the compressor, due to the lack of oil there from not running, on top of the normal pass-through (albeit very small) with any hoses.

Refrigerant, whether it's R12, 134a, 1234YF, or propane out of your grill tank, naturally passes through any rubber hoses, and the shaft seal over time. The rate is so small it is undetectable, until a few years pass. With my '07 Silverado it was 7 years - 2014. My $500 leak detector detected no leaks whatsoever, but system performance wasn't what it was when new. A top-off of about 6oz. fixed that. That was 7 years ago now, and it needs another shot.

I've got a '86 Grand Marquis, and a '93 Volvo 940, both running on R12. The Marquis system was completely redone - replaced with all stock components, aside from a modern parallel-flow condenser. This thing makes us shiver on a 95° super humid day! It's AMAZING. The Volvo isn't quite as impressive, but is MUCH better than friends 940's running 134a. It has terrible performance at at stop. When I say terrible with R12, it's 57° vent temps on a 90°+ day. The Marquis manages to keep things in the low 50's to upper 40's when at a light. The 940's I've seen on 134a were all in the mid 60's when stopped. No good! But rolling down the road, you have to move the vents off of you on a long trip - it gets uncomfortably cold when they're aiming right at you. I couldn't own a vintage car without A/C. My mantra is, EVERYTHING has to work ... except for emissions related components, but you didn't hear that from me. 😉

[thehackmechanic]

@Smithsonite, yeah... in truth, I have a Winnebago Rialta (a VW Eurovan with a Winnebago camper body) that, every spring, "just needs a recharge." I've never been able to find the leak, I top it up, it lasts all summer. But, in general, when someone is trying to sell a car with non-functional a/c and says that it "just needs a recharge," that's almost never true. If it did, they'd "just" top it up and sell it with working a/c.

[61Rampy]

Something that anybody who plans to recharge their A/C for ANY reason should know is to STAY AWAY from the crappy refrigerant that so many auto parts stores sell. What I mean is any refrigerant that contains stuff in it that is so-called "stop leak" is extremely BAD. The stop leak may seal leaks, but it also plugs up the condenser passages, the TXV or orifice tube, and certainly doesn't do anything else any good. It can also ruin recycling machines, to the point that its cheaper to buy a new one, than fix the old one. There are kits out to determine if a system has stop leak in it, but the ones I've used were of questionable value.  A decent A/C shop should also have a refrigerant identifier machine, which can tell you if you have some weird stuff in there, along with air and hydrocarbons. Hydrocarbons usually come from using crappy R12 replacement refrigerants that use a propane base. While propane (R744) makes an excellent refrigerant, it has this nasty tendency of exploding or catching on fire, and is NOT legal for automotive use. Just buy pure R134a with no sealant, no dye, no nothing! Maybe dye is OK, but you only need a few ounces. Several cans of 134a with dye is gonna be too much for most systems. 

[61Rampy]

While I'm on my soapbox, I would advise to stay away from those cheapo "suicide kits" sold alongside that crappy refrigerant.  A set of Harbor Fright gauges would be a good investment instead.  Can taps can be purchased at A/C supply houses, and probably NAPA (not a sponsor). OK, I'll shut up now.

[mbr2000]

Enjoyable and informative article. I need to take your advice and get a bottle of nitrogen for my next job, which will be installing a Vintage Air system in a 69 Chevy pickup. As for "All it needs is a recharge," I once added nearly a can of R134a to a friend's 8-10 year-old Nissan system that hadn't been touched since new. To my amazement it was still blowing cold air the next summer! Must have been a very slow leak indeed.