When the centrifugal switch fails to close, the main winding of the motor will be overheated.

Explanation:
The centrifugal switch is an important component in single-phase induction motors. Its main function is to disconnect the starting winding from the circuit once the motor reaches a certain speed, typically around 70-80% of its synchronous speed. This is necessary to prevent the starting winding from continuously being energized, as it is designed to provide the initial torque required to start the motor.

If the centrifugal switch fails to close, it means that it does not disconnect the starting winding from the circuit even after the motor reaches its operating speed. This leads to several issues, including overheating of the main winding. Here's why:

1. Continuous energization: With the centrifugal switch remaining open, the starting winding remains connected to the power source even during normal operation. This results in continuous energization of the starting winding, which is not designed to handle prolonged periods of current flow.

2. Increased current flow: As the starting winding remains energized, it draws additional current from the power supply. This leads to an increase in the overall current flowing through the motor, including the main winding.

3. Overheating: The main winding is not designed to handle the increased current caused by the continuous energization of the starting winding. As a result, the main winding becomes overheated due to excessive current flow. This can lead to insulation breakdown, short circuits, and ultimately, motor failure.

So, when the centrifugal switch fails to close, the continuous energization of the starting winding causes an increase in current flow through the motor, leading to overheating of the main winding. This can result in motor damage and ultimately, motor failure.