First, the chosen "Waterproof Cooling Fan" must be able to provide enough exhaust volume (speed), under the conditions of high temperature hot air inside the cooling equipment; when the temperature is relatively low and less when hot air is to do the opposite work. Secondly, the position of the sensor should be installed at the selected note to the sensor in the proper position, as far as possible so that the sensor can be clamped directly to the surface to be cooled. AC fan operation, a temperature-controlled "Waterproof Cooling Fan", will run at a faster rate higher if the thermistor temperature sensation; and at lower temperatures, it will operate at low speed; in these higher and lower middle AC fan speed will almost never due to temperature change. AC fan temperature change is slow, "Waterproof Cooling Fan" speed of change is slower, will not suddenly change the AC fan speed and noise. The reaction time mainly depends on the length of its sensor to the heat-sensing sensitivity. Therefore, the speed of the AC fan speed control based primarily on the heat sink temperature difference between the sensors and transmitted automatically adjusted.