- A cooling fan relay is used on vehicles that have an electrical fan to cool the engine. The function of the cooling fan relay is to convert a low voltage signal from either the electronic control module (ECM) or a thermostatically controlled sensor.
- The cooling fan relay takes the low voltage signal and internally switches the relay “on” to allow battery voltage to be supplied to the radiator cooling fan. By using a lower voltage signal to control the relay, there is less stress on the rest of the wiring and charging system. When the fan relay does not work, then the proper signal will not be received and the fan cannot cool the system down.