With the "Micro Cooling Fan" application and environmental temperature changes, and sometimes requires a different fan speed to meet demand. Some manufacturers specially designed adjustable fan speed cooling fan, manual and automatic modes. Manual is designed to allow users to use "Micro Cooling Fan" low speed in the winter low-noise, high speed to get good cooling effect during the summer. Automatic thermostat radiator general class with a thermostat sensor, capable of "Micro Cooling Fan" of speed, high temperatures will increase the speed according to the current working temperature control, low temperature, then reduce speed to achieve a dynamic balance, so that the cooling effect of wind noise and maintain an optimal combination of points.