Cause Tiny Cooling Fan does not turn

"Tiny Cooling Fan" in our daily lives of the most common household appliances, is a fan driven by the motor rotation, so that the air speed up the flow of household appliances, is generally used to allow air to circulate cool or hot weather. In the summer of life, "Tiny Cooling Fan" role is very large, and even necessary for our lives. Electric persistent the problems will arise, of course, fans will be, then the fan did not turn what causes it?
1, poor maintenance, long-term lack of lubrication.
2, with a long time due to wear and tear.
3, caused by overheating "Tiny Cooling Fan" does not turn.