The purpose of this SAE Recommended Practice is to provide a service procedure for retrofitting a CFC-12 (R-12) system to HFC-134a (R-134a) while preserving performance and integrity of the air-conditioning (A/C) 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 CFC-12 (R-12) and HFC-134a (R-134a), including refrigerant recovery/recycle (R/R), service manifolds, vacuum pumps, and charging equipment shall be used to preserve the purity of the refrigerants and the mobile A/C systems. This procedure will minimize release of refrigerant to the atmosphere, and will preserve the integrity of the recycled CFC-12 (R-12) and HFC-134a (R-134a) supplies. This document applies to A/C systems used to cool the passenger compartment of automobiles, light trucks, and other vehicles with similar CFC-12 (R-12) 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. A/C systems used on mobile vehicles for refrigerated cargo that have hermetically sealed systems are not covered by this document. This document is only complete when combined with the requirements of SAE J1657 "Selection Criteria for Retrofit Refrigerants to Replace CFC-12 (R-12) in Mobile Air-conditioning Systems."