That's not true about R-134a. Many people have done the conversion and it works just as well as the original. You can buy R-134a at Wal-Mart for a reasonable price, or you can try to find someone who still has R-12 for $30/lb. You should do it now while you'll probably be replacing things anyway. R-12 isn't getting any cheaper either, or easier to find.

When I purchased my 75, it was A/C equipped, but was not hooked up. The compressor was froze and the belt had been removed long ago. While I felt I could do all the work myself, I found out quickly that air conditioning is a specialty. I was lucky enough to find a fellow worker that does air conditioning on the side. After everything was said and done, I was glad to have someone that knew what they were doing perform the repair. I had to purchase a new or rebuilt compressor, which is easily found. You could probally go to any corvette parts distributors, but I found everything I needed at Autozone. I converted the freon over to R-134a. The R-12 is colder, but not easily found these days. Since your system hasn't been hooked up in a while, I would suggest that the whole system be cleaned. The EXPANSION VALVE will need to be replaced along with the seals and o-rings. I had some inside ducting missing, on the drivers side and other ducting clacked from just being over 25 years old. I replaced the missing ducting, fixed the cracks and resealed anything that would cause A/C leakage. The high speed on the blower fan also did not work, so I traced down the wiring (from my trusted laminated wiring diagram)and found a fuse blown under the hood. Even after the A/C system was rebuilt, the temp was 60 degrees at the vents. After fixing all my leaks I as able to get it down to under 50 degrees. After some more research I found that chevy had a problem with the water shutoff valve. It seems as if the automatic isn't very automatic anymore, so I installed a manual shutoff valve in the return side of the heater line. This by itself dropped the temp down to around 35 deg F. It's still not the greatest at cooling you, but at least now I can stand driving on a long trip. Short trips, I pop off the tops and enjoy the wind. Let me know if any of this helps. I have other information on this subject as I spent almost a month on just the air conditioning on my 75.

thanks for all the info bill. i'm making the a/c my winter project,and i'm sure you'll be getting a ton of e-mails from me for now i'm gonna do the most pressing projects,change all the fluids,tune-up,seat-belts and horn and just drive her with the t-tops off! sun,vette,t-tops...life is good

I am constantly working on my 75. Most of time, just because she is fun to work on. My next project is removing all the interior and re-dying it. Heck, that was my reason for purchasing a Air Compressor and paint gun. If you every have any questions, just drop me a email. bill0830@yahoo.com or post here. Happy vetting......

thanks again bill and keep