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2/16/09 1:09am - Original Message: 'AC concerns'
rod7515 Lifetime Member
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Red Lion, PA - USA

Vette(s):
1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic

Joined: 10/27/2006
Posts: 1172
when I bought my 74 vette it had just been changed over to the r134 because of the cost involved. I have plenty of the r12 so if I pull the system to vacuum, add r12 oil can I go back to the r12 or is it more complicated than that. Also the air isnt strong from the vents so I need to figure out where the air is leaking because the fan has all the speeds. Any suggestions as I would like the AC to function properly. Thanks
Rodney


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2/16/09 2:07am - Reply: 'AC concerns'
tb2k82ce Lifetime Member
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Lemon Grove, CA - USA

Vette(s):
1982 C3 Collectors Edition 44000 miles, sat in the sun most of it's life, My wife purchased it for me for fathers day in 2007 from her girl friend that had it for 19 years. It is on the road again. I'm retired but it is now my daily driver.

Joined: 10/17/2007
Posts: 2007
I know that the other way around is a no no.  I was told the washers (rubber/neoprene) and a couple of other things are changed.  I do not know if r134 system can take the r12 for sure.  If know one else has a fore sure answer I can try to get hold of a friend (we both lost our jobs at the same time about 5 years ago but I think I can find him) that did conversions and ask.  I have some R12 also but have not gotten around to seeing if my 82 air conditioner works yet.  I hope it does as the conversion is costly I'm told. 

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2/16/09 2:14am - Reply: 'AC concerns'
DaveM Lifetime Member
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Flanders, NJ - USA

Vette(s):
1982 Black, ZZ4, Hooker Side Pipes, 3.55 Rear, Rebuilt & upgraded 700R4, All new suspension, brakes, & new Charcoal interior.

Joined: 1/27/2004
Posts: 2530
Check with Terry (my7T1) PM him, he's in the  AC business.

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2/16/09 11:59am - Reply: 'AC concerns'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19447
The problem with doing this either way on the '74 is the VIR(valves in receiver) system. That is where a lot of the oil will be, and it's danged hard to get it out without removing the VIR, which is a major pita itself.
If your car has been converted to an orifice type system, then it ain't so bad. Either way, you'll need to drain the compressor of as much oil as you can, and replace the dryer(if it has been converted).
The seals used for 134 will handle R12, as far as I know, since they are better to start with.
Why do you want to go back with R12, anyway? I know it feels cooler than 134, but...if the system is working properly, it will cool just as well.
Getting all of the air to come thru the vents is a wonderful fantasy for most of the Shark cars. It can be done, tho, with a little attention to details under/behind the dash.
Most of the tubing connections were "close" from the factory, and "sealed" with small strips of foam rubber. Over time, the seals disappear, and now "close" ain't even in the picture!
I've seen vent connections that were at least 1" apart, with gaps you could stick your arm in(well...at least a couple of fingers...).
If you get all of the tubing connections sealed, it's a HUGE improvement in air-flow from the vents. You also need to make sure the air doors are all in the correct positions for whatever vent you want the air to come out of(heat/A-C/defog).
It's a major deal, but certainly worth the effort.

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2/16/09 12:08pm - Reply: 'AC concerns'
corvette440hp Lifetime Member
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Joined: 7/2/2006
Posts: 8205
The efficiency is a bit different between R12 and R134A. R12 boils at -22 degrees F. R134A boils at -16 degress F. R12 uses mineral oil, R134A uses PAG oil. The "O" rings are different on the R134A due to the oil. The pressures are slightly higher on R134A. Now to your question; You can revert back to the R12. The oil will work as well as the different drier/accumulator. The only diffenence  would be in the compressor cycling switch. It will shut off the compressor clutch at a slightly higher pressure. It's hard to give more information to you without my knowledge of the total changes that were made from the original R12 to the R134A conversion. I'm not trying to confuse you, if you feel that you have the R12 and the time...go ahead and experiment with it. Hopefully you have a vacuum pump and gauges to do the work on the system.  I've never have known if anyone has done this.  corvette440hp2009-02-16 09:13:56

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2/16/09 10:43pm - Reply: 'AC concerns'
kstyer Lifetime Member
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CUYAHOGA FALLS, OH - USA

Vette(s):
1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!

Joined: 12/2/2003
Posts: 6410
The R134a molecule is smaller then the R12 molecule.  Thats why you need better seals.   All 134a seals and equipment will hold R12 with no problems at all.
 
And yes, if the restrictor device (orifice, VIR, etc ) has been changed, and the pressure switch has been changed, you need to change them back.  Other wise, just the oil and R12 swap will work very nicely.
 
BUT>>>>>>   Why would you want to do this?????   Just use the R134a.  If you have R12, sell or give it to someone who had not done the change over.   You will be better off in the long run.   Some day you will be out of R12 and want your car cold again, and need to revert back to what you have now.


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2/16/09 11:48pm - Reply: 'AC concerns'
my7t1 Lifetime Member
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Dorr, MI - USA

Vette(s):
71 Colonnade Hardtop Coupe Torch Red with black interior originally L48 built to push around 360hp

Joined: 8/21/2002
Posts: 2580
First question I have is, where did the refrigerant go? If the system leaks you need to find out where and fix it. From there I have to agree with Joel and Ken. Why would you want to change back? If the system was retro-fitted properly, I would continue with 134A. Doesn't seem like it would be worth the time and expense to change back. In my years of business, I have never heard of anyone retro-fitting a system from 134A back to R12.  However it is possible. The oil difference is the most important factor.
My .02 "T"


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