1, "24V DC Cooling Fan" poor maintenance, long-term lack of lubrication. Fan shaft section is to ensure that there is oil, otherwise the blades will not drag in the above motives. If it is your own home, you can choose to turn off the power, then struck fan, if the rotation stiff, then basically no lubricant of.
2, with a long time due to wear and tear. If a fan with a long time, the motor will be losses, after the motor bushings wear will be very easy to burn.
3, "24V DC Cooling Fan" caused by overheating fan does not turn. The device in the fan motor is inside the motor will have a thermal circuit breakers, if local coil winding short circuit, will increase the amount of heat in a short time, in which case the motor will "strike" does not move up.
4, start capacitance becomes smaller. When the fan with a long time, the capacitance is reduced, resulting in the motor starting torque becomes small, unable to drive the load.
5, "24V DC Cooling Fan" electrical failure problems, such as line damage.