About Autocoolguy
To regulate the RPM of your fan, Autocoolguy uses pulse width modulation. Autocoolguy sensor tracks the temperature of the radiator outflow and modifies the fan speed to maintain the outflow at a constant 15 to 20 degrees below the thermostat temperature. The thermostat can control engine temperature in this way. For best results while adjusting the black knob, use a laser temperature gun and place the red dot on the outflow area and on a black, dull surface. Due to temperature errors, stay away from shiny chrome surfaces. Do not hurry and take your time in this situation. The engine temperature should be solid once you have made this change. You can observe how your fan's RPM is affected by speed and motor load.