AC conversion

[markowyo]

Finishing my '64 Cutlass total restoration (yeah!), have only the AC to put back on and together. Most folks are saying convert to 134a. I am interested in advice folks might have to offer. There's lots on the internet, kind of hard to ferrett out what's on point. Mine has been disconnected and off for a while, but all openings always capped.

What I am hearing is ... get a new compressor (old one liable to leak now or soon after), new dryer, rinse all tubes and other parts with denatured alcohol and dry completely with clean air to remove old oil and any residue, replace old nitrile rubber lines with impermeable tubing, new o-rings, new 134a oil.

That doesn't sound too bad. Am I missing anything? Any tricks of the trade I might employ?

Thanks in advance for your advice.

[rocketraider]

Is it a factory or aftermarket system? If you're going the 134a route with a factory system, you'll need to get a POA (also called Suction Throttling Valve) that is set up for 134a. 1964 still used a vacuum operated STV which can be rebuilt if needed. There's companies that do it.

A cheaper/better alternative if you're not obsessed with originality is to convert the system to a cycling clutch and orifice tube system. There's kits for that too. Most people won't notice the cycling switch in the tubing. It's more efficient too since the compressor is not running full time.

Compressors, dryers all are available set up for 134a conversions.

DNA will work or there's specialty A/C flush chemicals. The key is DRY. Clean air is not necessarily dry air. I think you'd want to pull vacuum on the system for several hours to remove all moisture once you got everything back together, then let it sit overnight to make sure the system is tight. 134a will find openings R12 won't pass thru.

With the different pressure/temp characteristics of 134a, when you charge the system with it a good rule of thumb is to start off with 75% of the normal R12 charge capacity i.e. if system used 4 lbs of R12, use 3 lbs of R134a. Check pressures and dash outlet temps and adjust charge as needed. You may need to add or remove it to get the coldest outlet temps within accepted compressor discharge pressures.


#####


Now's as good a time as any to say that I think the whole R12 ozone hole fiasco is hooey. What I do think, and this is strictly my opinion and conjecture, is that the original R12 patents were about to expire and DuPont was going to lose their lucrative R12 licensing royalties.

They had developed R134a and couldn't find a market for it because, face it, R12 worked great and was cheap, so no incentive for anyone to use the more expensive and less efficient R134a. When not even Honda (who were/are notorious for using different auto chemical formulations than everyone else) was interested, DuPont lobbying money went to work on Congress and the EPA. Result? R12 was legislated out of use by the Kyoto Protocol, based on what I consider questionable government-sponsored science. Hey, if there's an agenda, make your research give you the desired results to further that agenda.

Also interesting that the countries involved in KP are the only countries who banned R12. It's still made and used all over the world, out of reach of US patent law.

[joe_padavano]

Wow, and I thought I was a cynic...

Politics aside, the one big advantage to converting to 134 now is that when you need a freon top-off in the future (and you will), you can buy 134 and do it yourself. With R12, you're at the mercy of the EPA and a high-priced shop who will tell you that they can't fill it up unless they rebuild the entire system again (at great personal expense).

See, I really AM a cynic...

[Bluevista]

I'm getting ready for the same deal, although with the heat gain from the Vista windows and huge interior it will probably be a little tough to cool, maybe I should get a cab divider window. I was doing a job at a frat house and they moved a bunch of old refrigerators they had out next to the dumpster. I went to the truck for some tools and there was this scrap- scrounging wino guy ripping the coils off the backs of them using a hatchet, gas hissing out everywhere. The government should really start a program to give gas recovery units to these homeless scrap metal guys to reduce the evil global wa..oops it's called climate change now, that covers anything, who's cynical?

Allan

[markowyo]

Thanks Rocketraider. Mine is a factory system which I am converting. I prefer original looks, but am willing to trade for better performance.

Didn't realize I would need a new or modified POA. What is the modification there?, and any idea who does that (reliably)?

Have never heard of the "cycling clutch and orifice tube system" changeover. Again, do you know any reliable sources of information and kits?

Thanks, the old '64 is looking like its fresh off the showroom floor, now I want it to travel cool.

BTW, I am an atmospheric scientist ... if you want straight scoop about ozone depletion and climate change, not the polarized and politically motivated stuff abounding today, drop me a line.

Markowyo

[Olds64]

Cycling clutch and orifice tube systems are the systems used by GM in later cars. I know they used it in the 80s and 90s. I am not sure if they were using it in the 70s.

They work really well. I converted an orifice tube system on my 91 Buick Estate Wagon to R134a. Don't forget to replace the hi and low pressure hoses on your system before you pull a vacuum on it.

[FTW65W29]

I did a conversion on an 87 Chevy Silverado that I use to own. I did everything that Rocketraider recommended. The only part that I did not install from the factory system was the orifice tube. I went with a pop off valve that was designed for this type of system. I was told by the A/C parts house that this will allow the system to cycle more often. They told me that once the system pressure builds up to a predetermined point the compressor kicks off and bleeds down slowly as a result of the orifice tube. With the pop valve, once the compressor kicks off the valve bleeds down quicker thus resulting in quicker recycling of the system. Bottom line, your system will keep your vehicle cooler. I did not notice any difference between the R12 and 134a as a result of making this change. In fact after the conversion, I did not have to add any freon for the next couple of years. The next owner, co-worker, only had to add a partial can the 3rd year out.