The Facet Auxiliary Fan Switch - 75684 is a component used in automotive cooling systems. It is designed to control the operation of auxiliary fans, which help to cool the engine when it is running at high temperatures. The switch is typically located near the radiator and is activated by the temperature of the coolant. When the coolant reaches a certain temperature, the switch will turn on the auxiliary fans to help cool the engine. This helps to prevent overheating and potential damage to the engine. The Facet Auxiliary Fan Switch - 75684 is a reliable and essential part of a vehicle's cooling system.