You'd have to be new to this hobby, or a little inattentive, to not be aware of the excellent choice and availability of aftermarket air conditioning and heating systems we enjoy today. In fact we have just such an install coming up on the project '49 Chevy in the not-too-distant future. But what if you have a Fifties or Sixties car and don't want to go to the expense of ripping out the factory air conditioning to replace it with a modern aftermarket version? Is your old A/C system viable nowadays? Can it be upgraded? What's this about Freon becoming unavailable?
Whoa, let's take a step back and we'll answer those questions and more after we explain a little more about refrigerants, availability, and the Environmental Protection Agency. Older A/C systems use a refrigerant commonly known as Freon, the DuPont trade name for R-12. After studies proved R-12 to be damaging to the ozone layer, the EPA phased out its use and then banned its manufacture in 1996 with its replacement, R-134a, first being used in new cars in 1992, and used almost exclusively by '95. Which means that 'our' type of cars all use an obsolete, and now scarce refrigerant. The problem is R-12 and R-134a don't mix, and while the former is still available, it may not be for much longer. Occasionally, though you may not be aware of it, any R-12 you can get may have been smuggled from outside the US or is an illegally manufactured blend, as reserves of R-12 manufactured prior to the EPA ban are getting low.
As R-12 cannot be mixed with any other refrigerant, converting to R-134a involves removing the R-12 using approved recovery equipment, as venting into the atmosphere is forbidden, before new refrigerant can be added. If your cooling system is working efficiently and holds its charge there is currently no reason to retrofit it for R-134a as an R-12 system is designed to work with that refrigerant and offers its best performance with it, and while supplies last, staying with R-12 is logical. Even if it leaks, or requires minor repair, recharging it with R-12 is probably still the preferred option, as converting to its successor will typically see the cooling performance reduced. However, repair may not be an option if the parts are no longer available, though there are suppliers that can help. Old Air Products specializes in vintage and antique A/C systems and may be able to supply heater valves, expansion valves, receiver/driers, evaporator coils, blower motors, compressors, switches and reservoirs for many early models from various manufacturers. They even carry rare NOS parts for Ford and GM cars, as well as offering complete new retro-looking underdash A/C units.
While it's possible to retrofit an older A/C system to take R-134a, sometimes seals, hoses, the compressor, receiver-drier, and even the condenser need to be changed. The components in the A/C system are comprised of the compressor, condenser, evaporator, orifice tube, thermal expansion valve, receiver-drier and accumulator. If your car has an orifice tube, it will not have a thermal expansion valve, as these two devices serve the same purpose. Also, the system will use either a receiver-drier or an accumulator.
A compressor designed to run with R-12 may not be compatible with R-134a. The different refrigerants have different chemical properties, with R-12 using a mineral oil to lubricate the compressor and R-134a using a PAG oil (polyaklylene glycol lubricant). OEM compressors including some Keihin, Panasonic and Tecumseh versions cannot be retrofitted because of this. Also, because R-134a raises the discharge pressure from the compressor, some lightweight versions will not work for long using R-134a.