finally with wood to knock on the shaft to make sure it concentric

If the capacitance becomes small to cause the fan does not turn, you can remove the capacitor capacitance change with a new model, it is recommended to select 20% larger than the original capacitance,standing fan will have a better rotation effect. After adjusting the shim shaft axial clearance much of a problem, you can choose disassemble the motor. But I remember back when the motor is installed, you must pay attention to the rotor and the bearing concentric, lubricating screws diagonally slowly tightening, and finally with wood to knock on the shaft to make sure it concentric. If it is because of an electrical fault, you can check the wiring of the lines, electric stand fan sometimes damaged wires can fix issues