All classic car original air conditioning systems were filled with dichlorodifluoromethane or R-12/CFC-12 Freon. Even newer cars used the standard R-12 until the EPA, under section 609, in an attempt to reduce atmospheric ozone depletion, mandated that manufacturers phase out its use by the end of the 1994 model year. An environmentally friendlier substitute, tetrafluoroethane or R134A, was selected as the new industry standard, and plans were to phase out R-12 manufacture entirely by 1996. At the same time, new regulations regarding recharging of the older air conditioning systems on classic cars were also mandated. Original R-12 systems were to be retrofitted to accept the R134A refrigerant. The changeover kit depended on the original manufacturers’ components, but basically consisted of adapters for connecting the older R-12 charging ports to the new R134A charging hoses and manifolds. A filter drier changeover was also done and once the old R-12 was purged from the system (hopefully through an MVAC refrigerant recycler), a new R134A-compatible PAG oil was added to the system for lubrication before the system was refilled.
Prices for old R-12 skyrocketed as production was reduced and sales of R-12 were restricted to certified air-conditioning recycling specialists. This caused many classic car owners who wanted to keep their A/C system original turned to household R-22 Freon while it was still available. R-22 Chlorodifluoromethane was commonly found in household air conditioning systems, as well as refrigerators and freezers and in tractor-trailer reefer units. It was a passable substitute, but generated much higher engine compartment temperatures than the original R-12. The EPA soon realized that R-22 was being put into R-12 systems, and eliminated the production of R-22 in 2003. Like R-12 though, you occasionally see someone with an old container making a tidy profit by sitting on a stockpile for a few years. R-22 in household refrigeration units is now substituted with R502, but it is not recommended for automotive use.
refrigerant_02_800R134A or HFC-134A became the accepted standard, because it has no potential of ozone depletion and has similar (but not equal to) cooling abilities to the R-12 and R-22 refrigerants. Many classic car enthusiasts have stated that their original air conditioning systems, once changed over and refilled with R134A, do not blow as cold as they used to. Unfortunately, there is not much anyone can do about this. With the new EPA mandates, some driver comfort has to be sacrificed in the name of a more environmentally friendly and safer replacement refrigerant. Anybody who grabs a can of air to blow off their computer keyboard is using HFC-134A to do it. Computer air has fewer lubricants in it than the conventional R134A.
In the future, look for even R134A to be replaced with even more friendly substitutes. Recent European environmental standards have called for a new Freon formulation known as R152A. The good news with this new formulation is that it can be retrofitted into an R134A system without modifications and it actually blows slightly colder air than its R134A predecessor. R152A is slightly less dense than R134A, so it can theoretically contribute to better fuel economy as well. The bad news is that it is a Class 2 flammable gas, similar to bottled acetylene, hydrogen and methane. It would not be a good thing to get it too close to a spark plug wire or a hot exhaust manifold.
The other new alternative to R134A is HFO-1234YF, which has similar properties to R134A but meets the new European global warming standards. Each of the above-listed refrigerants has a global warming potential rating as well as an ozone depletion rating, and as of yet, the HCO-1234YF is the only refrigerant that meets both EPA and European standards. HFO-1234YF is also a Class 2 flammable gas although slightly less flammable than the R152A. Other Class 2 refrigerants found on the market, but not recommended for automotive use include R1143A, R142B and R143A.
Whatever refrigerant you end up using, it is important that the old system be completely purged before attempting a changeover, and old refrigerants be removed into an MVAC recycler, preventing them from escaping into the atmosphere. The MVAC recyclers are required equipment today for any A/C service bay or car dismantling operation that repairs any automotive A/C system or breaks down old A/C-equipped vehicles for scrap. Although classic car owners will extol the virtues of keeping the old R-12 in their automotive A/C systems, the supply market will eventually dry up and one of these alternatives will have to be used.