R12 is not illegal. It is in phase-out, meaning it is available in reduced amounts each year. As a result, the price of R12 is now over $100 per pound (most recharges take 1 - 3 pounds), thus conversions to R-134a are getting more popular. For some older vehicles, the receiver/dryer will not work with R-134a and therefore conversions are very expensive, requiring new compressors and receivers. The average 80's and 90's vehicle can be converted for a few hundred dollars (mostly labor).V8Cobrakid said:R-12 is technically "illegal". Or, at least illegal for any licensed A/C mechanic to supply.