Some Franklin Control Boxes have only black colored capacitors while some have both black and gray capacitors. Why?
Black capacitors are start caps. Start capacitors are used to start the motor and are then switched off by the relay. Gray or silver colored capacitors are run caps. Run caps help start the motor and then continue to provide energy to the start winding after the start capacitor turns off, making it an auxiliary or helper winding. This extra energy in the auxiliary/start winding improves the operation of the motor and makes it slightly more energy efficient.