Q: How Do Drive and Serpentine Belts Work?

Accessory drive belts are used to transfer rotational motion from the crankshaft to the other accessories on the engine. The driven accessories include the generator, power steering pump, air conditioning compressor, secondary air pump, and the water pump. There are two types of accessory drive belts: V-belts and serpentine belts.

V-belts were used all the way up to the 1990s when they were replaced by serpentine belts. V-belts are shaped like a "V", which is how they got their name. These belts rotate on two or three pulleys to operate their respective accessories. Many older vehicles used multiple V-belts to operate all of the engine accessories. All of the V-belt pulleys rotated in the same direction.

Serpentine belts are so named because they follow a back and forth direction similar to the movement of serpents, or snakes. This is made possible by the fact that serpentine belt pulleys can rotate in either direction. As a result, there is usually only a single serpentine belt to drive all of the accessories on an engine. Serpentine belts use both the ribbed side of the belt and the smooth backside of the belt to operate the pulleys.