Automotive Air Conditioning Information Forum

Looking for parts for my ‘66 Corvette a/c setup. Is there any overlap with other GM vehicles for things such as the suction throttling valve (STV)? Can I use one from a 62-65 Cadillac or Buick? Or were they unique for the Corvette?

Are you going to keep it R-12, or do you intend to convert it to R-134a? if the latter, you'll need to re-calibrate your original POA (STV) valve to the "newer" refrigerant.

If your original POA valve is intact and rebuildable, why replace it? Several professional rebuilders with an Internet presence can handle replating and rebuilding that valve for you, as well as recalibration to R-134a, which is typically done as part of the rebuilding process unless you specify otherwise.

Since your car probably has an A-6 compressor, which was not meant to cycle, I would stay away from the so-called POA Eliminator Kits, which DO cycle the compressor.

I intend to keep R-12 in there. I just had the STV (prior to the POA), A-6 and drier rebuilt with a brand new evaporator installed. It was extremely difficult to find a new piston for the STV. A few places still have the diaphragm and o-ring kits. I am just worried if something happens to mine I may never find another in a few years.

I didn't realize at first that your '66 Corvette has an STV, similar to the one I had years ago on a new '62 Impala/283/Powerglide with factory A/C. The STV was hidden under the right-front fender in the engine bay and operated manually via a cable controlled by a horizontal slider on the lower-center-dash A/C panel.

I think your classic restored-parts concerns are mostly unfounded. One parts restorer with whom I'm familiar is located in Tampa, Florida, and in Grapevine, Texas. They specialize in restoring your own original GM parts, not previously restored parts by someone else from another car. IMHO, these people know what they're doing, and I expect that they'll be around for a long time.

As far as R-12 is concerned, I believe that it's a smart move to keep it as originally designed by GM, especially a second-generation Corvette. However, R-12 continues rising in cost and is difficult to get, but it's still available from various sources. If worse comes to worst, you can convert your original system to R-134a (also becoming increasingly expensive) in the future with a little help from the experts mentioned above.

JohnHere wrote: ↑Sat Feb 10, 2024 1:39 pm Are you going to keep it R-12, or do you intend to convert it to R-134a? if the latter, you'll need to re-calibrate your original POA (STV) valve to the "newer" refrigerant.

If your original POA valve is intact and rebuildable, why replace it? Several professional rebuilders with an Internet presence can handle replating and rebuilding that valve for you, as well as recalibration to R-134a, which is typically done as part of the rebuilding process unless you specify otherwise.

Since your car probably has an A-6 compressor, which was not meant to cycle, I would stay away from the so-called POA Eliminator Kits, which DO cycle the compressor.

I have never understood why some claim the A6 should not cycle. GM had plenty of OE A6 systems that cycled and it still lasted forever on them. I had an 1983 G20 van with 250K miles on it still on its OE A6 and it was a CCOT system from day 1. I converted that system to R134a in about 2002, had new barrier hoses made for it from front to rear and replaced the front seal in the A6 with the newer style intended for R134a. That A6 lasted until I later swapped it out for a HD6 when I put a TBI 350 accessory setup from a 1992-1995 van in with a 400 hp Vortec 350 I built. Only reason I wemt away from the A6 is because I could not stand V-belts.

My understanding is that the A-6 was not designed to cycle due to its small-diameter clutch, not because of the compressor itself.

What say you, GM Tech?

JohnHere wrote: ↑Sat Mar 23, 2024 8:37 pm My understanding is that the A-6 was not designed to cycle due to its small-diameter clutch, not because of the compressor itself.

What say you, GM Tech?

I have always heard that myself, however GM and Ford used millions of them in cycling clutch orifice tube systems from the factory and many of them were also dual evaporator systems. In real life I have never noticed those failing any more often than the ones that ran constantly with a STV or POA system. I have probably converted 20-30 systems to R134a with a cycling clutch using a POA or STV eliminator kit as well with great results. I have worked on systems with A6s in tractors that cycled the clutch with a thermostatic switch in the evaporator case as well and even those A6s lived good long lives. I saw an interesting failure once on a Jaguar V12. Ever opened an a/c system full of gasoline? A6 did not care for gasoline as a lubricant much and one of the only ones I have ever seen lock up and smoked the clutch in the process.