From HKS: Many vehicles have cooling fans controlled by the stock ECU. If a lower degree thermostat is installed, engine temp will still remain high at low speeds where there is little or no air through the radiator causing unstable engine temps.

This unit can control one fan at two speeds, or teo fans at one speed, it can be set to turn on and off at any temp. It has a real time display for water temp, using the factory water temp sensor. A peak hold function memorizes and display s the max temp values. A built-in buzzer alarm function and blinking backlight, warn the driver if the set temp is exceeded. This allows the driver to tell whether the temp is rising or falling by the rate that the backlight blinks.