About the Fan Just like other major components in the car, the radiator cannot work on its own. It has supporting parts that help it perform its function more efficiently. In order for the radiator to reduce temperature of the water and coolant mixture that goes through the engine, it needs airflow that absorbs the heat and assists evaporation. Radiator fans are used to draw the air towards the radiator and help in the cooling process. High performance radiator fan may be used to replace your OE product for more efficient cooling. They allow more air to circulate around the radiator and they need less horsepower to operate too, making them ideal for your radiator fan replacement. Also, These Slim Fans have an ultra slim design so the fan can be installed easily against your radiator, in the most convenient position to allow for more leniencies for other aftermarket parts. About the Relay Relay is an electrical control device that usually used in automatic control circuit. The relay in fact is an automatic switch which uses a smaller current to control a larger current. What's the Relay Used for Compatible with almost all automobiles and devices equipped with a 12V DC power supply. Like starter kills, power door lock/actuator control, change a low current output to high current, Add ignition/accessory outputs,control motors/other electronics. It is also suitable for automobile used for control, alarms, horn, headlight and more. About the Relay Pins Pins 85 & 86 - are used to turn 'on' the relay. You need a positive (+) and negative (-) power source to turn on the relay. - Pin 85 - is usually negative (-) - Pin 86 - is usually positive (+) Pin 30 - is either a (+) or (-) source that feeds Pin 87 or Pin 87a Pin 87 - when the relay is 'on': Pin 30 and Pin 87 are connected