Not being an A/C guru (or any other type of guru for that matter) based on what your describing there is a slow leak in the system that needs to be located.  Guessing it is also running on R12 refrigerant.  My advice would be to find an old school repair shop that specializes in radiator and A/C work.  A dye can be added to the system and then looked for to determine where the leak is.  Such a slow leak may be tough to find.

Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

The same shop has done the recharge and dye has been added each time I've had it recharged, best I can recall 2 times. Last time I told the shop owner I want this problem fixed; they say they can't find a leak. I trust the shop but I'm beginning to wonder if they are thinking to them self's more money in the recharge than a sure fix. Maybe I should have a Chevrolet dealer look it over but that can get really expensive, pretty fast. I've seen a lot of times the seals on the compressor are the culprit of the leak but as I noted the compressor looks like could be new. I wouldn't hesitate to buy a new compressor if that solved the problem, after about 2 or 4 recharges the new compressor would be a cheap fix.

Since there is oil in the air conditioning system, a leak should manifest itself over all this period of time by a oil leak. I know that is the fact when the compressor shaft seal starts leaking. You will start to see a buildup of an oil film there. If the shop can't find evidence of a leak with the dye in the system then there could be a leak in the evaporator core. In order to see that, you would need to remove the housing in the engine compartment. Yes, it can be done without pulling the engine because I installed factory air on mine without pulling the engine.

1973 L-82 4 spd

Thanks for the idea on the evaporator core, I'm going to look at the compressor myself this morning and see if I can see any oil build up around shaft. Might be hard to see as tight as everything is under the hood. Don't they use a special type of light to see the leaks, that's always been the impression I've had. I didn't say it my first post about this problem but the second time I had back to the shop and complained about it, they did a little more looking into things and found some Oring seals in the air conditioning lines that needed to be replaced. Without looking at that bill, I do recall that maybe up to 2 each Orings had been replaced in the lines. That alone made the ac last longer, but only 2 or 3 years more in my opinion I still have a problem in the system some place, Don't you agree? Or am I out of line with my expectations with an ac unit in a 42 year old car?

Do you know what type of refrigerant is being used? 134a has a tendency to leak more than R12 due to using higher pressures, and having smaller molecules to begin with. 134a in older systems with original hoses will leak...period. Older style hoses were not meant to contain the smaller molecules of the 134a, nor were any of the seals. A/C compressors use a ceramic seal on the compressor shaft, also, and those will leak if the system is not run consistently, meaning, not driven much. If the car sits a lot, it needs to be at least started and run once a month, and the A/C system run at the same time, to keep everything in working order. This will not completely stop the leakage, but it usually slows it down some. 

Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thanks Joel, I was also wondering if the problem I have is not my doing by not running the car and ac enough, it sounds like it may be my fault more than a problem with the system. Without looking at the bills I'm sure that the new type of refrigerant was put into the system. Now let me ask you this. In your opinion, can this problem be solved with me having a new aftermarket compressor and lines put on, or am I wasting my money for the amount of time the ac will last. Or am I better off just getting the system recharged next spring and use the ac and drive the car more often? Just from what you have already stated it sounds to me like I'm going to be better off doing the last, but I'm truly interested in opinions.

Just looking at the receipts on the Vette and ac problems, it has been retrofitted with R134A refrigerant and the last time it was recharged was last year about this time. I decided to go check out Wally World and bought a name brand A/C Pro R-134A professional gauge and hose kit and 2 cans of R-134A refrigerant for a grand total of $48.91. That's one h**l of a lot cheaper than a shop recharge. Can't hurt anything to try it myself, after all it's not working now. I don't think I can go wrong with the kit I bought, it has a trigger dispenser and gauge on it. Kit cost me 24.97 and 9.98 a can for the refrigerant. Say some prayers for me guys and gals.

It looks like I may have solved my problems. I put 1 and 1/2 cans in and now have cool air, how long it last is another thing. Really don't matter next spring I'll check it out and add if necessary. It sure beats paying what a shop would get to do it. Thanks everyone that responded for your opinions and ideas. Have a Great day and Take Care. 🙂

If it were a daily driver, I would probably go ahead and "fix" whatever it needs to be reliable. If it's a weekender, or every now and then driver, then I would certainly just buy the freon and charge it when needed. 🤠

btw...I buy cases of 134a at Sam's Club here....they have a pretty good price on the case, and I always have some around the house when needed. Actually cheaper than buying from the parts suppliers....and I'm in the automotive bidness! Go figure.... 😎

Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Be aware that newer cars are now using R1234a, just noticed that on wife's 2018 Expedition.

1973 L-82 4 spd

I think that by me just driving the car more will solve my ac problems. I don't drive it enough and I know that's the main problem. When I bought the car it had been sitting in storage for years, the sticker on the plates was at least 6 years old, if not more. I'm not saying it hadn't been started, but obviously had not been on the road. The shop I use checked it out and we had some leaks. We put in a new aluminum radiator, water pump replaced all hoses and belts. Replaced oil pan gasket, oil pump, replaced the power steering's power assist control valve and other things. I'm not having problems with leaks any longer other than the ac. I know not driving it is the worst thing you can do; I also know you guys know life is busy. I just need to make more time driving it, and I will.