Look at the circuit diagram below.

The starting capacitor is broken and the motor can't start. Its main feature is that the motor makes abnormal noise.

A rotating winding should be added to the rotating magnetic field of AC motor, and the capacitor is an important part to adjust the phase.

Because this capacitor is generally an oil-based paper capacitor, it runs for a long time. Slow dry selling leads to a decrease in capacitance. Air-conditioning fan motors often have the same problem.

Of course, there are other problems: for example, there is too much smoke oil, and the viscous torque is greater than the starting torque (common in covered pole motors); For example, the problem of motor winding with starting winding and so on.