The majority of vehicle AC system warranty costs are a result of compressor replacement caused by excessive wear and seizure-related failures. In today's environment, compressor manufacturers can control manufacturing process well and maintain a stable product quality. Thus, compressor durability heavily relies on a durable AC system design. Both vehicle compressor suppliers have a variety of procedures and test methods to evaluate AC system and compressor durability. Often times, we still see very different compressor warranty return rates (one higher, the other lower) for the same compressor from the same production line in similar vehicle AC systems. In many cases, both AC systems passed vehicle and component durability tests. In addition, compressor manufacturing process quality was controlled well. The question remains why is there such different compressor warranty return rates? It drives one to think of a common index to characterize AC system durability level and thus link compressor warranty return rate with the degree of AC system durability.In this paper, vehicle drive duty cycle and AC usage, profiles are discussed. AC system and compressor durability tests are reviewed. Compressor warranty concern chance (CWCC) is introduced and discussed. CWCC is developed from a compressor compression index  that describes compressor working status in AC system. By evaluating vehicle AC system and component durability test data, CWCC is calculated by coupling with vehicle AC usage profiles.With this method, it can proactively analyze AC system and compressor durability test data to develop an index of compressor warranty concern chance, thus providing us a high confidence level for a robust AC system.