"Waterproof Cooling Fan" Speed is the number of revolutions per minute of the fan blades, the unit is rpm. Fan speed is determined by the motor inside the coil turns, voltage, number of fan blades, angle, height, diameter and bearing systems. Speed and "Waterproof Cooling Fan" quality is not necessarily linked. "Waterproof Cooling Fan" fan speed can be measured by the internal speed signal can also be measured by the outside. With the application and ambient temperature changes, and sometimes require different AC cooling 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 a low speed in the winter low-noise, high speed access to good cooling effect in the summer. "Waterproof Cooling Fan" automatic type thermostat radiator with a thermostat sensor in general, according to the current working temperature control fan speed, high temperatures will increase speed, low temperature, then reduce speed in order to achieve a dynamic balance , so that the cooling effect of wind noise and maintain an optimal combination of points.