I have recently purchased an 81 C3, 30k mile Red on Red coupe. Absolutley love it. Before purchase, and especially after, I have had the car on my lift going over it with a fine tooth comb. Very impressed with the overall condition. I purchased the car from the original owner, known it all its life, and he was extremely picky with it. My question is, in our triple digit Texas heat lately, the A/C cools, but doesn't get cold. I measured 51 degrees at the outlet register in center of dash. PO insists it still has R12, and has only been added to once. He doesn't have a supply of R12, and I don't either any longer. Considering the conversion to R134a, and all that that entails, but also it is kinda neat that it is still R12. What would yall do? R134a or Stick with the R12.
BTW, I have found NO other concessions or alterations on the car. Belts, Hoses, emissions, etc. all GM and functioning as designed. This car is stored from Labor day till Memorial day, and will only see minor weekend cruiser duty then. The T-Tops are claimed to have never been off, as he didn't want them to start leaking. I have not removed them either. Just enjoying for now, and considering the direction. I understand its not a desirable year, but I am very proud of the originality none the less. Thanks in Advance.

Lane

 

If it were me I'd stick with the R12. If it needs any at all it won't need much to get it cooling the way you'd like it to. I have a 79 C10 that I converted and I still regret it. Not as cool as when it had the R12 system. Considering the expense to change it over and what it may cost for a recharge I think you're better off keeping it original.

 

LowBuck, welcome to the forum.

This is an excellent place for information.

In my opinion, I would stay with the R12. While it costs a little more to service than 134 you will save the cost and time to convert, thus cheaper in the end.

As for the T-Tops, be careful if you do decide to take them off. The rubber seals may be partially adhered and could possibly rip or tear the rubber seals upon removal.

I won't agree with the statement that an 81 is not a desirable year.

I happen to have one that I think is quite beautiful and in similar condition to yours.

BTW, where at in Texas might you be?

 

Oh, and we like pictures here. Lots of pictures.

Post a few up of your ride.

The link below will assist you in posting those pictures:
https://www.corvetteforum.com/forums...tep-guide.html

 

Thanks for the replies. Good to know im not crazy for wanting to stick with R12.
Vette in the Veins - Im in Littlefield, Tx. Northwest of Lubbock.

I currently have no intentions of taking the tops off, other than possibly to apply some type of treatment to keep them from sticking. I haven't worked up the nerve to attempt it yet. LOL. Still researching how I want to do that.

I've had an eye on the car for several years, my wife found out PO was ready to sell, and sent me on a mission. I have been pleasantly surprised with the condition, but it seems now I spent a whole lot more time thinking about how I want to approach maintenance, etc on the car.

 

I'll see what I can do about pics, I'm not very computer savvy. May have to get the kids to help. I have some on my phone, but I am looking for a place to get some better pics before we put it up for the winter.

 

Keep the 12. My experince with 134 in another vehicle ,when your not moving you aren't cooling.

 

Just going through the same on my 81. When I purchased it 2 years ago from the second owner they replaced most of the system except for hard line and condenser several years earlier. It was still R12 and I would say cooled efficiently, not to the point of freezing cold either, but I was happy with the cooling. Then when I had my engine pulled to be rebuilt the machine shop broke loose one of the A/C lines and lost all the R12. They agreed to repair and when I got it back they converted it to R134a without my approval. The A/C never cooled below 78 degrees air temp from vents again. I finally got tired of taking it back to the shop complaining and leaving it there only for the owner to keep saying " the pressures are fine".

So I finally starting troubleshooting myself a few weeks ago and found the pressures were way off and very high and the shop never fully evacuated all the old oil out along with never changing the accumulator. So at this point I found an A/C shop to work with me, evacuated the system and will vacuum the system and refill after I replace everything myself. I removed everything from the system except the evaporator which tested with no leaks, but I will flush it several times before installing all the new parts. When I say all new parts I mean replacing compressor, accumulator, rubber and hard lines, orifice, new Parallel Flow condenser and installing a relay so the AUX fan stays on when A/C is in Normal or MAX.

Hopefully after this the A/C will be running cold again, it gets pretty hot here in Florida, although I like driving without the T-Tops, it is nice on the hot, sticky humid days to turn on the A/C. Just wanted to share what I have gone through, hopefully you can get the system running cold again with the R12 and not need to replace everything.

 

How's the new install going Reaper19?

 

Hey Street Rat how's it going? Well I have everything pulled out and preparing for installation of all the new equipment. I ordered new radiator seals and ran into a little snag. I thought the seals were too thick at first, but upon further inspection noticed the radiator was reinstalled with too small of a gap on the bottom between the radiator and support frame when the engine was put back in. So I am going to loosen up the radiator brackets, slide it away from the frame and install the new seals. I am hoping to break away from my daily job after working this weekend, flush the evaporator and start installing the new parts. Hopefully complete the job by the end of next week.

I'll update my previous thread when I get close to completing.

 

Stay with the r12. 134 just does not work well with these old systems. You can get plenty of r12 on ebay for about $30-35 per can and to be strictly legal, you can get a license online for $20.

 

I recently got the A/C working in my '79. It needed a new compressor and accumulator. It's now charged with 3# of R12 (per spec) and cools very well here in the awful summer soup we call "weather" in SE Missouri. Humidity removal is better than in most new cars.

Every A/C guy I know says that R134 will not cool or dehumidify as well in these old systems even with a different condenser design and the proper expansion valve.

I too say to add R12.

Technically the system should not leak at all--even over decades--so you might want to have the existing charge recovered and the system carefully checked for leaks.

 

may need new o-rings and a new charge of r-12, that is what usually starts leaking, or the compressor seal goes bad. does it have a sight glass like my 76 has on the high side alum hose??/ if system is on and there small air bubbles going thru the sight glass, it needs a charge until the bubbles go away.

 

Many things can effect this temp.

If the heater core shut off doesn't work well then the heater core is still hot in the car. Many have installed shut off valves on the heater core lines to insure that no heated water gets to the core.

If you still have the stock cooling fan then it is not pulling very much air across the condensor at idle. Try idiling it up to 1200 - 1500 RPM and try that temp again.

The hotter or more humid it is outside the higher the duct temp is going to be.

If you are not in "max" ac then it will be warmer as the duct air is having to be cooled from the outside air temp down to the duct temp you are measuring. In max the air is recirculated in the car so the temp drop is the same but from a lower starting temp making the duct outlet temps lower.

 

When I purchased my '81 the a/c system was not functioning correctly. So I don't know how good the R-12 could cool. I totally rebuilt the system this year with R-134a. I'm using a kit that contained a Sanden compressor. I also replaced the old condenser with a parallel flow type.

I live in Central Texas where the temperatures are frequently around 100 degrees during the summer. I have a black car with the smoke glass tops and a black interior. I have been more than satisfied with the cooling of the a/c system using the R-134a. But I want to stress that I have nothing to compare it to.

I realize that the older Corvette systems use different parts than my accumulator based system. They certainly may cool better with the R-12. I don't know. I am simply stating that an R-134a system can indeed cool in a satisfactory manner.

I'm glad you guys still have access to the R-12 freon. I'm not advocating using one or the other. You should use what you can afford, feel comfortable with, and what works best for your system.

 

Thanks for the replies guys.
No, my car does not have the sight glass.
I have started looking for replacement R12, a friend owns a local shop that can recover R12, clean it, dry it, and re-use. He is helping me look for a Shop size R12 container. On a related note brought up by ReelAv8tr, I did notice today that the heater core shutoff valve is the only part on the underside of the car that does seem to have a little corrosion. When I tested it with a vacuum pump, it seemed to stick slightly, then moved to the closed position. The vac gauge read approx 16", then when the valve started to move, it dropped to 10" and recovered when the valve closed. I took it up to 21" and it held over an hour, so no apparent leakoff, but the sticking concerns me. Im thinking I need to replace the hot water cutoff valve.
BTW, when I tested outlet air temps, I had the controls on Max, and holding the idle at 1000 rpm per guidelines in the Service manual. The Engine cooling fan clutch kicked in after a few moments, so air flow seemed good. I am not aware of an aux cooling fan on this car.
Anway, I will be replacing the hot water valve, and topping of with R12 in the near future. I will post results. Thanks again for all the ideas.

Now I'm wondering if there is a Silicon based rubber treatment for the rubbers on the T-Tops? I would like to apply to the door seals also, since when opening the doors, they seem to stick a little also. Could this be from PO using ArmorAll on the rubber gaskets? He was obviously a big fan of ArmorAll, but I can say the interior is flawless whatever his efforts included.

 

 

 

I use and have been using silicon spray for years on the rubber seals on my car doors. It does keep the rubber from drying out. T-tops same deal.
This is usually what I have on hand and use.

https://www.menards.com/main/tools-h...4451781964.htm

 

Wow, really nice looking engine bay! Like a time capsule.