The reason Waterproof Cooling Fan does not turn

Priority thought was "Waterproof Cooling Fan" No motor lubrication, shaft portion to be lubricated, yesterday I was in this case, the fan motor is mounted on top of the drag or not, but after I removed, the shaft can operate normally, indicating that the motor do not spoil. How to judge "Waterproof Cooling Fan" in oil out? Is after disconnecting the power, you gently struck fan, found that rotating a little stiff, indicating that the oil is gone, and turn up very ease, indicating oiled, this are other reasons not to turn up. Second, you have to consider "Waterproof Cooling Fan" with how long, the motor loss, after the motor bushings wear, it is easy to burn. Motor with a long time, it will also make the motor resistance becomes larger, with a load capacity becomes low, making it impossible to drive the blades rotate. Motor overheating will cause deterioration of the motor with a load capacity, the motor active power becomes low, making it impossible to drive the load.