AC Loses Freon Problem

Q: AC Loses Freon Problem

I’ve got a 1969 with AC which slowly loses it’s freon. All O’rings were replaced by the previous owner about 4 years ago. When I got the car last year – it blew kinda cold. This year, it just blows. Yes, the compressor does kick in. I would say that the hoses are probably all original. Would this be an ideal time to convert to a newer “freon” and if so, what would need to be replaced. Recommended sources of parts and technical “tips” are appreciated!

A: Napa and may other parts stores sell a conversion kit to convert to 134a. It comes with new O-rings and Ester oil. While your replacing the O-rings and hoses, spray brake cleaner into the evaporator and condenser and blow with compressed air. This is to help remove excess oil that may not be compatible with the new oil. Brake cleaner drys very fast and is a good solvent.

There is a plug on the bottom of the compressor. Remove the plug and drain the old oil and add the new oil. make sure you lube all the new O-rings with the new oil before you re-assemble the system. You’ll also have to replace your receiver-dryer.

But, before I would disassemble the system, I would try to find the leak. If a service center cannot find a leak, the cost of a re-charge may not be as bad as you think considering everything you are planning on replacing.

The interesting point is you say the compressor is coming on but the air doesn’t blow cold. It’s my understanding that the compressor will remain off or will contentiously cycle on and off if the system charge is too low. You may want to check this out a little more closely.

I just had my whole firewall box apart and I couldn’t believe how plugged the evaporator was. This would definitely affect the systems ability to cool. This may be part of your problem.

A: I wuld disagree about using brake kleen to blow out old oil, its too harsh on old rubber. Used denatured alcohol, it too evaporates quickly. Actually you should replace any rubber with “barrier” hose, which is designed for 134a. Seems as tho 134a will leak in places R-12 wouldnt. It will actually permeate rubber hose as the molecules are smaller. Theres a real good site on conversionsby the EPA under alternate refrigerants. Dont know the URL. use search engine to find.

A: I need to point out that pressure/cycling switches were not yet being used in 1969, so the compressor runs with the power from the controls, even with no freon. Those switches came on the scene I believe in the late 70’s or early 80’s.

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