Several field problems are anticipated with HFC-134a systems. To be evaluated and clarified are the impacts upon: compressors and systems of chlorine based solvents left in the system from flushing or parts cleaning; mixing in CFC-12; mixing the new lubricants with mineral oil; the effects of certain lubricants and HFC-134a's high hygroscopicity and others. The whole industry should share information and endeavor to maintain the reliability of the new systems from a service engineering standpoint.STARTING IN 1991 the ozone safe HFC-134a refrigerant is expected to replace the conventional CFC-12 in car air conditioning systems and in model years 1994-1995 the major portion of the market will be the new systems. The components/elements and parts used in the new air conditioning systems will embody different designs with new materials which are now considered to be compatible with the new refrigerant-lubricant mixtures. Most components and parts are now being developed with new materials by specialists in each area using leading edge technology. But for two to three years, the high volume market exposure of the new AC systems will be the only way to collect sufficient knowledge of possible reliability problems and failures which can actually occur. Some of the common practice that has been established with the CFC-12 systems will not be applicable to the new situation.