WHen I bought my 74 coupe the AC compressor was missing. My question is this: can I use a later model copressor which is much smaller and lighter with my stock evaporator and condensor? They are in good shape. I have installed new wiring harnesses and checked out the controls, etc. What other changes would be required to make it work? I would also like to update it to F-134 or whatever that new stuff is.

Thanks in advance for the help.

Ron Cantrell

I think the answer is yes you can, but you will need new brackets and possibly new hoses. Most of the aftermarket compressors use individual male threaded hoses, while the original had a double, o-ringed manifold held on by a center bolt. I don't think the weight loss is worth the effort. I persoinally would stay with R12, but whichever way you go put a new dryer on it. If it has been open very long you will probably need a new VIR valve, or retrofit to a cycling type system (my choice). Good luck with it.

Thanks for the reply. I don't have any brackets either, that's one reason I was thinking about the change. I understand, I think, that the 74 compressor runs all the time. What is involved in converting to a cycling system?

Ron Cantrell

I understand that there is a part that replaces the VIR valve and has a low-pressure switch like the 78 up stuff. I have never put one on a Corvette, but have done a few 67-9 Camaro retros. If anyone has a source for a Corvette replacement, I would be interested in seeing it.

The only people I know that make a conversion kit is the Corvette Clinic in Sanford, FL. I don't have their number handy, but ask for Andy Petra. He has the hot setup for converting AC systems with all new brackets, compressor, wiring harness.

Later models use the A6 compressor, which is supposed to be more reliable. Ecklers sells the bracket for it, though there's probably someplace cheaper to get it. Right now would be a great time to switch to R-134a, while you have everything apart. R-12 isn't going to get cheaper or easier to get, and offers no advantages.

The mounting bracket is pretty easy to find. Most of the catalog houses have it. GM may still offer it.

I think the costs of fabricating news hoses will exceed the value of changing the compressor. Regardless, get new AC hose installed on your fittings and manifold. Any full service radiator or automotive HVAC place can do this. Cost me about $75. After 30 years of dry rot these will not hold pressure. I learned the hard way after watching a full load of R12 vent to the atmosphere 2 hours after the system was charged. The hose simply burst.

The components aren't really expensive. I bought a Delco rebuilt compressor for $125 (plus $35 shipping... it was 50 LBS). A Delco rebuilt VIR was $75 on e-bay. It was an extreme PITA to replace.

If originality is not a concern, switch to the cycling type valve. Again, readily available. Also, R134 works great, especially when you are starting from scratch.

Lastly, even when this is all working properly, interior comfort/discomfort is affected by many other issues, heat transfer through the floor, minimal air flow from the blower, HVAC mode doors that don't open and close, etc.

Getting the AC to blow cold is easy. Getting the interior cool is another matter.