HFC-134a is the refrigerant of choice to replace CFC-12 in automotive air conditioning. The purpose of this bulletin is to communicate the current test status of HFC-134a for use in new automotive air conditioning systems. It expands on the SAE Technical Paper (#890305)-“Performance Comparison of HFC-134a and CFC-12 in an Automotive Air Conditioning System” presented by Du Pont at the 1989 SAE International Congress and Exposition. Topics covered in this paper include: Environmental Impact Refrigerant Properties Heat Transfer Refrigeration Performance Materials Compatibility Hoses Elastomers Desiccants Metals Lubricants Solubility Lubricity Based on the test work completed, HFC-134a is not a “drop-in” replacement for CFC-12 in most existing systems. Depending on the system, certain design modifications may be required to achieve optimum performance and durability. The significant conclusions from this study are listed on page 12.