Genuine Daikin 157155J Fan Motor Capacitor is the 9 µF run capacitor that sets the phase shift for the fan motor so it starts cleanly and turns at full speed. When it fails the fan starts slowly, runs down, or stalls, and the unit can trip on rising head pressure as airflow across the coil falls. Because a weak fan capacitor often accompanies a tiring fan motor, pricing the pair together avoids a second trip — and the genuine 9 µF part keeps the motor on its designed phase angle where a generic leaves it running hot.