[dataway]

I'm going to try to get the OEM AC in my 68 GTO up and running again using R12 and original components. I've never done this before so advice will be needed. I'll be using the original A6 compressor if possible, if not then a new A6 unit from Alma.

Current status:
Have A6 compressor low miles original (needs at least clutch bearing)
Original Evaporator, looked great when I had it suitcase apart.
New OEM style condenser
New Drier (will still need to be replaces since I left the plugs out)
All the OEM suitcase related parts POA, expansion valve? etc.

Supplies and Tools
Plenty of R12
Robinair Vacuum pump
NOS Robinair vaccum manifold and gauges (made in USA)
3 charging hoses red, blue yellow from Robinair gauge kit
Purge valve made from a "T"
Scale to weigh tanks if needed.

My first task is to move some R12 from a 50 lb tank to a new 30 lb tank.
Here are photos of the tanks.

Full Tank


Empty Tank


Here are the hoses I have to work with.



Not really sure what hose to use. Plan is to draw a vacuum on the new empty tank, hook up a line to the full tank, purge the air from line and see how much I can transfer over without resorting to ice/heat.

That's the extent of my plan and knowledge at this point

Thanks

[gto4ben]

The pictures did not upload. Are you using a refrigerant recovery pump with the special tank for that purpose? Single use disposable refrigerant cylinders are not refillable. They have a check valve to prevent refills.

Have you purchased a supply of vacuum pump oil? After multiple purges, the vacuum pump will get contaminated with moisture and need to be replaced in order to get down to 100 microns or better.

Has the system been opened and exposed to atmosphere? If so, it will need to be flushed to remove contaminants. AC flush fluid is expensive so I used laquer thinner for initial rough flushing and finished with the AC flush. The good stuff apparently doesn't leave any residue.

Perform bench testing of the expansion valve and POA. The expansion valve has a factory mesh screen that is likely partially clogged and need s to be flushed and blown out. The POA needs to be checked. Bench testing instructions can be found on YouTube and other sites. I can provide some details if you have trouble finding info or making adapters.

I'm glad you have a new drier though if the plugs are out, you'll probably need another if it's been exposed to atmosphere for a long time. New driers are supposed to be compatible with both R12 and HFC134a. (XH9 dessicant).

Have you considered rebuilding your A6? Replacing the seals isn't too hard and you can use the new double lip shaft seal which is an improvement over the original ceramic seal.

[Bruce Meyer]

Consider using a Pro6ten compressor that Ames sells. It draws way less HP than an A6. Its also much lighter. It comes with oil for R134. You will need to drain it and put in R12 compatible oil. Easy to do. I run the Pro6ten compressors in both my GTOs. They work great

[dataway]

My empty tank is a new recovery tank with both fluid and vapor valves.

I do not have a refrigerant recovery pump, my plan was to evacuate the recovery tank and possibly use the "supply tank in hot water, receiving tank in cold water" method. I only need to get 20 lbs max out of the full tank and into the recovery tank.

I have a ready supply of vacuum pump oil

The system has been in pieces for years, all hoses will be replaced with new, condenser is new, new sealed drier will be used, I blew out the evaporator well before putting the suitcase together.

I'd be more than happy to rebuild (reseal) the A6 if that is advisable ... I have to put in a new clutch bearing anyway.

I will certainly consider using a Proten compressor if my A6 needs enough work that it would justify a new compressor.

My first step will be attempting to draw off about 15-20 lbs from the full cylinder.
Anyone done this before without a recovery pump? I see several videos on YouTube with people doing it fairly easily with a simple hose between tanks and using temperature to create the transfer pressure.

[jerry455]

I am doing the same with my 1976 Firebird. A/C has been apart for several years when previous owner installed a 455 into car. I bought it in 2018. I installed my bigger, badder, 455+ in, last summer and just finished installing the original A/C. I bought a new condenser, as the original had a lot of beat-up fins and looked questionable. I also bought a new desiccant kit, and it looks like the last bottle of A/C oil for R12 in the metro Detroit area. Older parts store and bottle was covered in dust, person there had no idea what it was for. They never heard of R12. A friend has an old Delco A/C charging station and R12, so he talked me into using it. I would have been happy to use R134 as I have used it in other older cars with great success. Hopefully in a few weeks we will have cold air.

[dataway]

Can anyone give me a quick description of those hoses?
Both ends are 1/4", one end open with a rubber gasket, the other end has what looks like a schrader valve setup.

I know I will be hooking up to Schrader valves on the AC, all the tank/gauge fittings are flare fittings ... so that rubber gasket is used on flare fittings?

I'm wondering if one of these hoses will work tank to tank, both tanks have 1/4" flare fittings .. I'm guessing I need a hose with 1/4" flare fittings on both ends with no Schrader valve thingie?

[Keith Seymore]

Subscribing.

K

[dataway]

Well, either end of the hoses seem to seal to a 1/4" flare whether it has a schrader valve in it or not. Of course my test was tying to blow through it, so not sure how valid it is Feels right snugging it up too.

[Sun Tuned]

I’ll share with you an idea I did on an 89 Chevrolet 3500 crew cab dually I have when I did mine. Let me just throw out some ideas and observations on this.

I didn’t like the way it cooled. Stock system with what they called an HR6 compressor. It worked but just like it was too small. It was. I looked it up. The old A6 was 12.54 cubic inches. The HR6 was half that at some 6.1 cu in capacity. It went away.

After I got the brackets for the old A6 for the 454 it was about to be on. Now everyone I ever heard that went to r134 just said the stuff don’t cool as good or it didn’t seem as R12. But the question I had was why? The new cars and trucks seem fine. Well I found the answer. Most people that converted from 12 to 134 kept their original condenser and flushed it or replaced with an exact new replacement.

Problem there is near every R12 condenser was a “tube fin” condenser. All the 134a stuff built after 1992 or so has a parallel flow condenser. It’s much much more efficient than the tube fin and the engineers knew this.its true that 12 is a better refrigerant but, it’s not that much better if you look at the data compared to 134. The reason the factory 134 cars did good was because the engineers understood that 134A needs a better heat exchanger(condenser) to get rid of the heat quicker. Hence the parallel flow condenser.

So I found one that was nearly same dimension as my original but a parallel flow version and installed it. Then I got to thinking… my truck has an orifice tube and gm used the white one. I see they have like 5… well turns out the difference is the colors and the orifice diameter of the holes. White is .072 ford used a blue one and it’s .067. So I put the blue one in.

Drew a vacuum on he thing and let it set for couple hours and no leaks. Charged it with R12 and I guarantee you that’s the coldest damn ac I’ve ever been around. Correct amounts. Never freezes up. Perfect normal operation.

Center vent air temp on the 3rd speed is 31/32 degrees in n end of July here.

[nUcLeArEnVoY]

^^^ Agree w/ Sun Tuned. You'll never get the most out of an R134a conversion unless you upgrade some components, most notably the condenser. R134a operates at higher pressure than R12, and higher pressure naturally produces more heat. Those old tube and fin condensers don't have the surface area to exchange that extra heat as well as a parallel flow design (which more closely resembles your typical radiator layout).

I would be curious to see how the parallel flow condensers work with R12, though. I guess they work amazingly well, based on Sun Tuned's results.

[Sun Tuned]

I need to fix the door rubbers and window fuzzies for sure. The passenger front window as my dad describes it is a pneumonia hole in the winter, so I can’t help but know that hot air is leaking in in summer also.

I will say this. A lot of folks don’t like the A6 compressor. They feel it’s too big, too heavy, outdated, blah blah blah.
I got a bounty on em at work. They’ll pull em off to put vintage air or something “modern” on and I been payin the guys 20.00 each for the core when it comes off. Most are original.

One day I’ll sit down and rebuild a few. Other than the seals theres not much to go haywire in em. Or I should say they’re either good or not. Obviously if the pistons get scored and such they’re toast. But I guess my point is you ain’t goin to GM parts counter and buying parts for em much anymore.

They suck a little HP off the engine I guess, but mine sure works quite nicely.


I think that’s why most don’t get a good result on some 134A conversions, I’ve seen a bunch come in at work and all that has been done is flush (maybe) new orings, and charged. Same original tube fin condenser still there.

I wanted to see what if???…. It worked nicely for me. I really think the R12 and the parallel condenser and a slightly smaller orifice tube dia to stall it in that condenser for just a tick longer to let the air on outside cool it a bit longer is the hot lick on the whole thing.

Even with the leaky passenger door rubber I’ve had cold reach up and turn the thing down to the first speed from the third(it has four speeds).

Kinda funny to watch.

[dataway]

Anyone know if one of those hoses in the pictures in the first post will suffice to transfer R12 from one tank to another?

[cmoc-bob]

Build video from Century Auto Air for the A6 - explains installation of both the OE seal and the double lip seal.

https://www.youtube.com/watch?v=0c7QXLNqgBU

[jahanzaib12]

Love seeing OEM AC systems brought back to life—there's something satisfying about keeping it original. If you're tackling this, I’d recommend checking all seals, replacing old O-rings, flushing the system, and definitely upgrading to compatible refrigerant if it’s an R12 system. Don’t skip the dryer/accumulator—cheap insurance. Curious to see how yours turns out, post pics if you can!

[burd]

I did my AC 20 years ago. It’s awesome keeping it all factory, neede a few parts but found them all. I had my orig Accumulator rebuilt. I’ll put that back on one day

[dataway]

I'll definitely be posting some pics. I'll have to so I remember what I'm doing.

Bob, thanks for the video link, going to watch it several times.

[dataway]

Well item one is complete.

I transferred about 20 lbs of R12 from the full tank to my transfer tank.

The setup I used is pictured below. I drew a 30" vacuum on the transfer tank, shut the valve. The hooked up a hose to the full tank, connected it straight to the transfer tank with the connection slightly loose. Cracked open the valve on the full tank till fluid came out on the transfer tank end then snugged that connection up ( did this to purge the hose).

Then opened both valves, about 11 lbs transferred in the first five minutes, then speed decreased slowly until it settled down at 20+ lbs. I had a heating pad strapped to the full tank but the tank never really got "warm" it just seemed to keep it from getting cold. Transfer tank was at room temp, about 65 degrees.

Then I shut both valves and called it good. I'll weigh the transfer tank after a week or so to make sure I'm not losing any.

[gto4ben]

The TARE weight of the R12 container is about 88.5oz (5.5 lbs). Subtract this from the current weight to see if you got most of the refrigerant transferred.

[dataway]

Ben, I only wanted about 20 lbs out of the 50 lb tank. I have to return the original tank and the remainder of the R12 to the owner.

Thanks for the tare weight of the gray tank, it didn't have one stamped on it. Just said 50 lbs Net Weight.

[dataway]

So I've got a new drier in the car, but as mentioned before, one of the ports has remained open for a couple of years now.

What I was wondering is if it can be saved. Couldn't I pull a vacuum on it (like a person would to evacuate an entire system) leave it for 30 mins, perhaps while warming up with a hair dryer .. seems like that could remove all the moisture.

I don't have to worry about any garbage in it as it's never been used.

Reason I ask is because it's one of the more expensive OEM style units.