(A second relay, sold separately, is required for two speed or dual fan operation). The controller monitors the engine temperature using a dedicated sender, or a gauge and its sender. When the engine temperature goes above a user adjustable set point, the fan is turned on with a relay. When the engine has cooled below a user selectable off temperature, the fan is shut off. Separate on and off temperatures can be set for the high and low fan outputs. The controller will also run the fan when the