A vehicle's drive belts are the link between the crankshaft and engine accessories. Belts are often referred to as "drive belts," because the accessories that they power are "driven" by the crankshaft.
The function of the alternator drive belt is to power the alternator, using the crankshaft pulley as the driving force.
There are two types of alternator drive belts. A standard, or V belt, is driven directly from the crankshaft pulley. The other, a serpentine belt, winds around various accessories like a snake, hence the name, powering the power-steering pump, as well as the alternator and water-pump.
An alternator drive belt should be tensioned properly for best performance and longest life. At the midway point of the belt, the deflection should be between a half inch and three-quarter inches when properly tensioned.
If the belt appears dry-rotted or displays cracking when flexed, it should be replaced. A glazed appearance on the inner surface is an indication that the belt is slipping and needs adjustment.
