The serpentine belt drives the accessories attached to the engine, such as the alternator, power steering pump, AC compressor, and water pump and radiator fan. Some vehicles use a single belt to drive all pulleys, whereas other vehicles may have two or three belts to drive different components. Belts can become cracked over time, however, newer belt designs do not crack when worn - instead the grooves on the belt become wider, potentially resulting in squealing noises as the belt goes around the pulleys. A broken belt can result in the vehicle being undrivable. Without the alternator, the battery becomes drained quickly. Steering becomes heavy with the power steering pump, and if the water pump is not turning, the vehicle will overheat quickly.
