Because as the ambient temperature changes, sometimes different speed "Micro Cooling Fan" to meet demand. Some manufacturers specially designed heat sink can adjust the fan speed, manual and automatic modes. Manual is designed to allow users to use a low speed in the winter low-noise, high speed to get good cooling effect during the summer. "Micro Cooling Fan" automatic type radiator thermostat with a temperature sensor in general, according to the current working temperature (eg heat sink temperature) automatic control "Micro Cooling Fan" of speed, high temperatures will increase the speed, temperature Low speed is reduced in order to achieve a dynamic equilibrium, so that the cooling effect of wind noise and maintain an optimal combination of points.