Motor capacitor

If the switch is always closed, the start capacitor is always in the circuit, so the motor windings will likely burn out.

[citation needed] Some single-phase AC electric motors require a "run capacitor" to energize the second-phase winding (auxiliary coil) to create a rotating magnetic field while the motor is running.

[1] Run capacitors are rated in a range of 1.5 to 100 μF, with volt classifications of 250, 370 and 440 V.[1] If a wrong capacitance value is installed, it will cause an uneven magnetic field around the rotor.

This causes the rotor to hesitate at the uneven spots, resulting in irregular rotation, especially under load.

The dual capacitor has three terminals, labeled C for common, FAN, and HERM for hermetically-sealed compressor.

[2] Round cylinder-shaped dual run capacitors are commonly used for air conditioning, to help in the starting of the compressor and the condenser fan motor.

These are extremely toxic and persistent chemicals with many long-lasting negative human and wildlife health effects.

If these capacitors leak or fail, PCBs can be released into the environment and will very likely result in extremely expensive environmental cleanups, and potentially, lawsuits.

U.S. EPA has much information on the correct way to test and manage these toxic chemicals in older capacitors.