The relay for the radiator fan is a type of an electric switch encased in the protective box of the relay, which oversees the power routed to the radiator fan motor. It controls the fan's electrical operation. When the ECU (Engine Control Unit) or radiator fan thermostat drives the decision to turn the fan on, a signal is sent to the relay that triggers it to close a high current circuit. Power from the vehicle's battery can now be redirected to the fan motor, thus enabling the fan to start. The low-current signals can now be supplied to the controls, and in turn, the fan motor draws a considerable current to operate. To reduce the greater portion of the electric current these relays are needed, these are called relay rad fan PLC.