The manual is designed to allow users to use a low speed in the winter low-noise, high speed to get a good cooling effect in the summer. Automatic class ships with a thermostat radiator thermostat sensor, it is possible according to the current operating temperature (eg heat sink temperature) automatic control "24V DC Cooling Fan" speed, speed is increased by high temperature, low temperature, then reduce speed in order to achieve a dynamic balance, so that the cooling effect of wind noise and to maintain an optimal combination of points. Some vendors specially designed adjustable radiator fan speed, manual and automatic modes.