Until it stops working, most people will never appreciate how important the A/C compressor is. The key component to your A/C system is the A/C compressor, if it is not functioning properly, your A/C will not work. Though the compressor can fail for a multitude of reasons, most commonly the two parts that will fail are the compressor motor its self or the clutch that engages the compressor to run will fail. With some compressors you can get away with just changing the clutch, others however you need to replace the entire compressor. When you have to replace yours, trust ACM A/C compressors.