The easiest way to convert from R12 to R134a refrigerant is by recovering any R12 refrigerant still in the cooling system, adding polyolester oil to the system and recharging the system to around 85 percent of its original capacity with new R134a refrigerant. Keep in mind that unless a vehicle's air conditioning system is leaking or broken, converting to R134a is not necessary, as the old refrigerant will continue cooling the vehicle safely and effectively.
R134a is a less efficient cooling chemical than R12. Typically, drivers who convert to R134a from R12 can expect a three to 15 percent drop in cooling efficiency after conversion. R134a is also tougher on compressors, and some less-powerful compressors fail after converting to the new refrigerant.
Converting to R134a is necessary because R12 refrigerant, also known as Freon, is no longer manufactured in the United States. Freon is lighter than air, so when the chemical leaks from an air conditioning or refrigeration system, it travels to the upper atmosphere. In the upper atmosphere, Freon molecules break down and react with ozone molecules, forming other oxygen compounds. This process depletes Earth's ozone layer, which is necessary for filtering ultraviolet light. R134a refrigerant does not react with ozone, and for this reason it is now the industry standard refrigerant for most cooling applications.