Crankshaft pulleys, often combined with the engine's harmonic balancer are what connect the crankshaft to the belts that run, among other things, the engine’s alternator and the air conditioning compressor. This pulley is located at the end of the crankshaft and sits outside the engine. Crankshaft pulleys don't really wear out but they can get damaged . If your car’s alternator or air conditioning compressor stops working, it could be the crankshaft pulley that is at fault, also. Crankshaft pulleys are fairly inexpensive, and we have a wide selection in stock.