The purpose of this SAE Recommended Practice is to provide a service procedure for retrofitting a CFC-12 (R12) system to HFC-134a (R134a) while preserving performance and integrity of the air conditioning system. The steps outlined in this procedure are complete when combined with good service practices and the vehicle manufacturer's recommendations (if available) for retrofitting their models. Separate service equipment, for R12 and R134a, including refrigerant recovery/ recycle, service manifolds, vacuum pumps, and charging equipment shall be used to preserve the purity of the refrigerants and the mobile air conditioning systems. This procedure will minimize release of refrigerant to the atmosphere, and will preserve the integrity of the recycled R12 and R134a supplies. This document applies to air conditioning systems used to cool the passenger compartment of the automobiles, light trucks, and other vehicles with similar R12 systems. Due to technical advancements in recent years, this procedure is recommended for common vehicle platforms produced in the mid-1980s and later. Vehicles produced before this time period may require additional retrofit requirements. Air conditioning systems used on mobile vehicles for refrigerated cargo that have hermetically sealed systems are not covered by this document. This Document is complete only when combined with the requirements of SAE J1657.