Tensioner, idler, and damper pulleys are critical components of a vehicle's belt-driven accessory system, found in both passenger cars and commercial vehicles. Located within the Service Parts > Major Service section of our catalog, these parts maintain proper belt tension and smooth operation of accessories like the alternator, power steering pump, and air conditioning compressor. Tensioners automatically adjust belt tension, compensating for wear and thermal expansion, while idler pulleys guide the belt and reduce stress. Dampers absorb vibrations, minimizing noise and extending the life of the belt and other components. Examples include MAN tensioner pulleys, such as MPN 51.95800-7520 and 51.95800-7494, as well as parts for John Deere vehicles.