Radiator Fan Controller Concept:

The Radiator Fan Controller utilizes proportional speed control based on thermal demand of radiator; this minimizes engine temperature fluctuation for improved engine performance. The Fan Controller utilizies a sensor in the radiator to measure the coolant temperature. The Fan Controller compares the coolant temperature to a reference and activates the fans at minimum speed to limit the coolant temperature to 140 degrees (F). This provides a coolant reserve that is 40 degrees less than the operating temperature of the engine. The thermostat in the engine, controls the temperature of the engine to 180 degrees (F) by opening only enough to allow the coolant to absorb heat above 180 degrees (F). As the ambient air or engine temperature increases, the Fan Controller increases the fan speed to maintain a maximum coolant temperature of 140 degrees (F). The only way that the engine thermostat can accurately control engine temperature is to have a coolant reserve with a lower temperature than the engine thermostat temperature. Accurate engine temperature control helps to lower harmful pre-detonation by keeping cylinder head temperature constant. Constant cylinder head temperature means ignition timing can be advanced more aggressively.

The Fan Controller is designed to fit in the original position where the relays are located, convenient for connections to the fans, temperature sensor and wiring harness. Independent electronic outputs for each fan provide redundant operation for reliability and simplified wiring. Even if one fan stops operating the other fan will increase speed to compensate. The current consumption of 2 high volume fans operating at full speed is approximately 20% of a starter motor during engine start. To alleviate the fan current at engine start, the Fan Controller delays the fan operation for 8 seconds when the ignition key is turned on, this allows full battery current for the starter motor. The Fan Controller also improves the  functionality of the fan indicator in the speedometer; "on" indicates the fans are operating and "flashing" indicates the fan fuse is open.