From "Waterproof Cooling Fan" inside the motor is concerned, it has internal protection devices, there is a thermal circuit breaker is part of the coil windings shorted, resulting in a sharp increase in heat, open circuit breakers, motor under such circumstances, the general strike . This rarely happens. Another is to start capacitance becomes smaller, although the nameplate reads those parameters, but a long time, the capacitance is reduced, resulting in a starting torque "Waterproof Cooling Fan" motor is smaller, can not drive the load. This simple, remove the capacitors, go to a new one, the same model should be no problem. But the best for a 20% larger than the original, and will get better results. Motor shaft axial clearance is too large can cause can not drag the load. If you are disassembling the motor shaft axial gap is too large to be adjusted by adjusting the shims. When installing "Waterproof Cooling Fan" motor, the rotor and the bearing must be concentric job, slowly tightening the screws diagonally want, and then use a screwdriver to knock wood shaft, making concentric.