A relay is an electrically operated switch that allows a low-power circuit to control a higher-power circuit. In the context of a cooling system, the relay is responsible for activating the radiator fan and ensuring that it operates at the right times to regulate the engine's temperature. The radiator fan helps expel excess heat generated by the engine, and the cooling system relay acts as a trigger, responding to the temperature changes in the engine.

    The cooling system relay is typically controlled by the engine control unit (ECU) or a temperature sensor. When the engine reaches a certain temperature, the sensor sends a signal to the relay, which in turn activates the radiator fan to cool the engine down. Once the engine temperature returns to normal, the relay deactivates the fan, ensuring that the engine remains within a safe operating range.