“factory air car, 66 belvedere, everything is there, connected, old but there...doesnt look to be in bad shape but anyways...i put in a new ac control unit, new heater/ac blower motor switch and go the fan working, so i charged the system up and wallah...air worked for about 2 hours...on way home, HOT AIR...so it leaked out three cans in about 2 hours time....”
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Let me take this in parts.... Do you KNOW that the refrigerant leaked out? Have you put a gauge set on it to verify that it is not still pressurized? Did you check the oil level in the compressor when the system was empty? Did you put R-12, or one of the compatible butane based refrigerants in it when you charged it?...
The reason I ask this is because you later state that you put dye in it and still can't find the leak. This would indicate a failed expansion valve in a pressurized system, as a leak would be quite obvious with a UV (black) light, but only if the system had oil in it (which caries the dye).
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"well when i got the car it had a stain which is still there on passenger side carpet of antifreeze/coolant...whichever."
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If I understand this right (correct me if I'm understanding you wrong), the stain is not related to (caused by) your latest A/C charge and failure. If so, the stain is from the failure of the heater core, or possibly, but somewhat less likely, the heater valve. Heater core failures are nearly universal in A/C cars, as the A/C subjected them to nearly constant moisture and corrosion.
A/C systems that have been dormant for long periods of time will cause the seals to dry out/crack, and fail when pressed back into service. R-134 does not "eat seals", but requires oils that are not as compatible with the old rubber seals, so if the seals are in poor shape, they will fail when pressed back into service. Plus R-134 is molecularly smaller than R-12, and will leak past the seals and hoses (just like a rubber Helium balloon will leak out the Helium over a short period of time, but will still look inflated).
A perfect R-12 system that has been properly converted to R-134 will need an additional 1/2 to 1 can per year under the best of circumstances, unless all the seals and barrier hoses were changed. If the system was dormant for a couple of years, you can have total leak-out in just a couple hours in an otherwise perfect (looking) system, no matter what refrigerant is used, but dye should show the leaks if the oil level is correct.
It's quite probable that I have owned more of these cars than anyone on this board, but I guarantee that I have owned more with A/C than anyone else. In all those cars, I have never found a failed evaporator, as that’s where all the oil accumulates/settles, so I highly doubt that you have an evaporator problem.
Seals are the most common failure area and are easily changed once you find the leak. The expansion valve is also quite common in a system that has not been run for a few years, as a newly charged system can cause accumulations of trash to jam the valve.
I like to say --- You’re not American if your car doesn't have A/C --- toung in cheek of course, but where I live, A/C is absolutely essential.