Andrew Markel discusses belt noise and flutter, and how to inspect the belt, pulleys and tensioners for these issues. Sponsored by INA.
Alternator pulleys are not so simple anymore. Many late-model vehicles are equipped with special pulleys that are engineered to reduce NVH (noise, vibration and harshness) and extend the life of the alternator. An Overrunning Alternator Pulley (OAP) has a one-way clutch mechanism inside the hub that allows the belt to turn the alternator in one direction, but allows the alternator to “free wheel” and spin at its own speed when the engine suddenly decelerates.