R12a vs. R134a 90 Vette

ringleader · 10-27-05, 03:53 PM

Thinking of changing system to 134a as my A/C needs freon. I would be interested to know if anybody had done this and if satisfied with the car getting cold.

korvettekarl · 10-27-05, 04:18 PM

I have installed a new 134A system in a 57 Bel Air and it got cold- 45 degrees. To change yours you will need new compressor and drier. Flushing the old system will be needed also. I am about to change a 64 Roadster to 134A. Still waiting on a new radiator before I start. The biggest problem is the condensor, they sometimes need to be a match to the compressor. You might call Vintage Air and ask them about it. They also have some good advice on thier web site about 134 and 12. Changing to 134A will save you money in the long run as R12 is getting VERY expensive and hard to find. Around 90 bucks a pound here in Vegas.

Moonunit 451 · 10-27-05, 06:41 PM

Freeze 12 is a direct drop in, no conversion needed and it works well. There are others too.

redvett · 10-27-05, 07:23 PM

Quote:

Originally Posted by ringleader

Thinking of changing system to 134a as my A/C needs freon. I would be interested to know if anybody had done this and if satisfied with the car getting cold.

If you want to save your self a lot of money and grief then stay with R12 because the R134 is really not compatible with the components in your vehicle. The hoses,condenser, accumulator, compresser,pag oil and of course the R134. The R134 has smaller molecules and will flow through the hoses faster than R12. The condenser is constructed differently for more efficency and all seals are not adquate with R134. The compresser is constructed differently and you would need another cycling and hi pressure switch due to higher pressure.
Having a competent mechanic check and repair any leaks and recharge would cost less and cool better.

tyrel · 10-27-05, 09:57 PM

There are a lot of myths surrounding the conversion, "it doesn't get as cold", "it's not compatible", etc. For one thing, the corvette used the same a/c compressor from 1989-1996, the nippondenso 10pa20c, which was well into the time when R134a became commonly used. Also the same evaporator, and I fail to see the difference in the condenser, maybe more fins in the later c4 or something. About the only difference would be the o-rings, and even then the stock o-rings don't leak nearly as much as some alarmists would have you believe. Nevertheless, it's a matter of maintenance when fully servicing the a/c to change the o-rings, HNBR rings are perfect for conversions because they are even more durable then the original stock ones. The low pressure switch is adjustable, and as far as the high pressure switch, my feeling is that, as long as the system is charged correctly, it can never get too high or it'll simply vent through the compressor relief valve. If the conversion is done properly, there should be only a few degrees' difference at your vent temps than using R12. Here are some sites that might help you:

http://www.acsource.net/acforum/

http://www.autoacforum.com/index.cfm?nocookies=yes

http://www.diynet.com/diy/ab_auto_ai...276708,00.html

bossvette · 10-27-05, 10:29 PM

thanks for the links, I have to work on the AC in three vehicles so I have some reading to do. getting tired of paying someone else to do it

redvett · 10-27-05, 10:33 PM

[quote=tyrel]There are a lot of myths surrounding the conversion, "it doesn't get as cold", "it's not compatible", etc. For one thing, the corvette used the same a/c compressor from 1989-1996, the nippondenso 10pa20c, which was well into the time when R134a became commonly used. Also the same evaporator, and I fail to see the difference in the condenser, maybe more fins in the later c4 or something. About the only difference would be the o-rings, and even then the stock o-rings don't leak nearly as much as some alarmists would have you believe. Nevertheless, it's a matter of maintenance when fully servicing the a/c to change the o-rings, HNBR rings are perfect for conversions because they are even more durable then the original stock ones. The low pressure switch is adjustable, and as far as the high pressure switch, my feeling is that, as long as the system is charged correctly, it can never get too high or it'll simply vent through the compressor relief valve. If the conversion is done properly, there should be only a few degrees' difference at your vent temps than using R12. Here are some sites that might help you:

I am retired from GM engineering and worked on the conversion to R134 and we used slave R12 vehicles and converted them to R134. Our tests showed that efficency was markedly reduced until we changed the condenser & compresser. The entire package has to be changed to get good results and reliability.

ringleader · 10-27-05, 11:46 PM

Thanks for your input and links, you have been very helpful, Is your redvette set up for 134a?
Thanks,
Ringleader

Moonunit 451 · 10-28-05, 12:47 AM

I didn't read the links provided, but I've read quite a few before. There is NO reason not to use an adequate "drop in" and save yourself a bunch of cash. This topic has been discusded many times. Oh yea, and Ive been useing Freeze 12 for 18 mos. very nice. Where is SunCR, I think it is, not that he will fully agree with me, but he knows this stuff. Do a search.

gmjunkie · 10-28-05, 08:30 AM

Quote:

Originally Posted by Moonunit 451

I didn't read the links provided, but I've read quite a few before. There is NO reason not to use an adequate "drop in" and save yourself a bunch of cash. This topic has been discusded many times. Oh yea, and Ive been useing Freeze 12 for 18 mos. very nice. Where is SunCR, I think it is, not that he will fully agree with me, but he knows this stuff. Do a search.

I'v Been useing Freez 12 for over 5 yr's Work's Great!! Depend's on what is Wrong with System on what I Do to it!! If Just Low I Freez 12 it!! If it has a Killed Comp. I Replace Compresser,Dryer (Acclum) Flush system and Change All O-rings,Put in a new orifice tube( Ford Blue #46031) or a Smart Tube(Self Adjusting VOV valve)!! and Retro!! If customer want's it to Look non-Retrofit!! (Classic Car's)I use Freez 12. with Ford Blue or Smart tube!! I Personly Like The Smart Tube!! It works alot Better at Low Speed's or Stop & go Traffic!! Don't Get me wrong the Blue tube work's way better than stock tube and most people Can't tell the Diff!! Unless thay get in a 2 hr.Traffic Jam on a Really Hot Humid Day!! For $30.00 it's Worth it to Me!! Use 10% less Freez 12 or 134a!! Freez 12 is a mix of 134a 90% and R-12 10% Homogenized so molecule's stick together!! (Like MilK and Cream!!) If retro fitting ajust Pressure sw's!!(non-ajustable) Replace!!

junk!!ps I replace Acclum-Dryer any Time have a System Open)................

Robertwav1 · 10-28-05, 12:25 PM

It's always an interesting subject and can't be discussed enough. The refrig forums have a blast with this also. The only thing I have against the 134a is that it is TOXIC....don't breathe it in. Enviormentally safe yes but raises hell with your organs. 12 on the other hand was unfriendly to the enviorment but it didn't bother anything living unless it's ignited. My opinion 12's the best...134a is known to block orifices because of it's wax like residue that is just the nature of the gas.

Greg Gore · 10-28-05, 12:47 PM

R-12 is still available if you know where to look for it (widely available on the world's largest Internet auction site). I don't know of a good reason to convert an R-12 system other than convenience. R-134 operates 90% as efficient as R-12 and in addition compessor pressures are elevated with it. R-134 will leak through porosity in conventional hoses and seals so these parts have required engineering revisions. I recently read a report that claimed more flourocarbons are released into the atmosphere from a single volcano eruption than is contained in all the world's refrigeration systems.

Regards, Greg

Moonunit 451 · 10-28-05, 04:27 PM

Quote:

Originally Posted by Greg Gore

R-12 is still available if you know where to look for it (widely available on the world's largest Internet auction site). I don't know of a good reason to convert an R-12 system other than convenience. R-134 operates 90% as efficient as R-12 and in addition compessor pressures are elevated with it. R-134 will leak through porosity in conventional hoses and seals so these parts have required engineering revisions. I recently read a report that claimed more flourocarbons are released into the atmosphere from a single volcano eruption than is contained in all the world's refrigeration systems.

Regards, Greg

Can't be related to AlGore. He'd have you extinguished for such comments

MBDiagMan · 11-01-05, 09:51 AM

Since the cars that require R12 are hitting the wrecking yards in massive numbers every day, the demand for R12 is rapidly dropping, and so is the price. I just got a 30 pound cylinder a few months back for $14.16 per pound delivered to my door.

By spending $15 and a few hours of time taking an open book test online, you can get the certificate needed that will allow you to legally purchase R12. This is by FAR the cheapest way to repair an R12 system. No need for changing any parts except those that may have failed anyway.

You can get the test at: www.imaca.org

Good luck,