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Gary meacham · 03-26-2006, 02:12 PM

Which refrigerent do I use????

engineer · 03-26-2006, 02:31 PM

run search, various opinions on this.

wheelspin · 03-26-2006, 05:35 PM

Use the gas it was designed for: R-12, which consistently produces lower discharge temps than 134 conversions.

Before you evac and refill your old system, replace all of the hoses with the current style barrier hose, use the crimp collars instead of hose clamps to secure the hoses, replace the drier, and the O rings located in the various fittings. I also recommend eliminating the POA valve, if fitted, and replacing it with a POA update kit that cycles the compressor clutch to control air temps.

Les

gtoformula · 03-26-2006, 08:20 PM

There was a guy that listed a post offering real Dupont R12 for a reasonable price. James Clevenhagen is the name. He is in San Diego. I bought several cans. They look just like the Dupont cans that used to go for $.99 (about forty years ago), but all the text on the can is in Spanish. Think it might have come across the border? If you can real Freon cheap (like from Clevenhagen) then you might consider using that as you won't need to change over charge ports and install a puller or pusher fan.

Gary meacham · 03-27-2006, 11:52 PM

Thanks all. I know 134a isn't really an option as I don't want an electric fan. I guess I'll need to find R12. It's aboput 60.00 a pound now, isn't it?

engineer · 03-28-2006, 01:52 PM

keep the original POA valve if it is working with the R12 freon. The cycling is not good long term for the A6 type compressor. for 134A, it does not matter as the limited cooling ability of 134 needs all the help it can get.

wheelspin · 03-28-2006, 02:02 PM

The A-6 is easily the most robust compressor/clutch unit in existence and the only way you will be able to determine if your POA valve works is to evac and charge the system, then evac and hold the gas while replacing/rebuilding the POA valve if it doesn't. Why bother when you can convert the system to a pressure switch and avoid the probability that your 40 yr. old valve no longer functions.

Les

johnsma22 · 03-28-2006, 02:35 PM

It is not that 134a is a less efficient refrigerant per say, it is that 134a is less efficient as a retrofit in an R-12 system due to the size of the evaporator. In a system designed for use with 134a, the discharge air temps would be identical to that of a properly functioning R-12 system.

John

engineer · 03-28-2006, 08:26 PM

the original POA valves are priceless these days and were optimum with the R12. the cycling switch did not come into play until the R4 compressor was introduced. Better to keep the factory design and originality than use some half designed switch, which was only introduced when the POA valves were not available or R134A was used instead.

Squidward · 03-29-2006, 03:51 AM

Cycling A6 compressors were used by GM in 1977 on the Firebirds, and this continued at least until 1981. The R4 was also available at some point during this same time period.

POA valves were discontinued in use due to efforts to reduce cost. CCOT systems are simpler and cheaper, but give up system effectiveness in return. POA systems maintain evap temps at a constant 32-36 degrees, as well as maintain a constant temp gradient across the entire evap cooling surface due to the equalizing line. It was a superior cooling design.

There are some efforts in modern vehicles to return to some of this type of design by using a compressor that adjusts to load so that it will stay running during low-load periods instead of cycling frequently.

It is possible to bench test a POA valve using air pressure so that it can be calibrated precisely for 26 psi (optimal pressure for R134). I've never done it myself, but I plan to play around with it since I have a 73 bird evap case and POA valve sitting in the garage.

I searched and found a link to a thread on a test setup using air and a set of gauges. http://www.autoacforum.com/messagevi...&threadid=6974

Last I checked, R134 was still cheaper than R12, but there's a major difference - R12 requires EPA certification to purchase, R134 doesn't.

I've read about the Mexican R12 - apparently there are a lot of issues with purity and quality control that is non-existent in Mexico.

69goatboy · 03-29-2006, 01:51 PM

What's the shelf life for the R12 cans? I've got about 5 or 6 cans that my father-in-law gave me when he moved. No idea as to how old they are but there is no rust or corrosion, they look brand new.

engineer · 03-29-2006, 02:04 PM

no shelf life on stored R12. if cans are intact and have contents, R12 is fine. Squidward, thanks for the confirmation. As you know, using a cycling switch is not the same as a CCOT system. If you must use a cycling switch, one should also replace the expansion valve with an orifice tube since the expansion valve was designed for a constant backpressure provided by a POA. I must not be the only chemical engineer here.

Brad B. Hillebrand · 03-29-2006, 02:46 PM

You can find lots of R-12 at the swap meets. Cost is about $30-$35 per can at the Midwest swaps.......

If you need some now and do not have any swaps happening I have a little stock pile and can sell you 6 cans. I have a swap at the end of April that I am going to that has lots so I can replenish. If you can't find any and can wait till the end of April I can pick some up for you as well.....you pay for shipping and what the vendor is selling it for.....if you are near Jefferson Wisc, you can get it at that swap at the end of april....

Brad

engineer · 03-29-2006, 04:21 PM

note: to buy or sell R-12 requires a license, even between private individuals as well as businesses. that can be done over the internet doing an open book test and about $25. An undercover agent at a swap meet can be a big dollar fine if caught.

Brad B. Hillebrand · 03-29-2006, 05:45 PM

Quote:

Originally Posted by engineer

note: to buy or sell R-12 requires a license, even between private individuals as well as businesses. that can be done over the internet doing an open book test and about $25. An undercover agent at a swap meet can be a big dollar fine if caught.

Get out of here!! Really?

I see these guys all the time, some with cases of the stuff, and not just one vendor but many. Last Jefferson swap I was at had at least 6 vendors selling. I often wondered why a license was not required so the first time I bought I asked the guy. He said he dosen't need a license if selling at a swap meet, not thinking more about it I purchased. Didn't ever ask again, just walk up and buy......I love America....

Can we get in trouble if we buy? If not who cares? They have something to sell that we need......

Brad

Squidward · 03-30-2006, 07:20 AM

Quote:

no shelf life on stored R12. if cans are intact and have contents, R12 is fine. Squidward, thanks for the confirmation. As you know, using a cycling switch is not the same as a CCOT system. If you must use a cycling switch, one should also replace the expansion valve with an orifice tube since the expansion valve was designed for a constant backpressure provided by a POA. I must not be the only chemical engineer here.

Eng,

I thought that the POA eliminator kits put an orifice tube at the evap inlet to replace the TXV, and replaced the POA with an equivalent piece of piping with a pressure switch plumbed into it to cycle the compressor. Of course, I haven't played with one, so I don't know if that's the correct assumption.

Do the POA eliminator kits retain the TXV? Wheelspin, how does your setup works?

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