The main function of automotive relays is to control high currents, as directly controlling high currents through switches may generate electrical sparks and cause danger. Automotive relays belong to switches that control high current with low current, and are a type of electrical component in automotive electrical systems.

Automobile relay is an automatic control device, and when the input quantity (such as electricity, magnetism, sound, light, heat) reaches a certain value, the output quantity will undergo a jumping change. The relays used in cars are typically used to control circuits and implement power paths in switch control circuits, such as lighting and air conditioning systems, heaters, horn signals, and fuel pumps.