Genuine Daikin 1718025 Capacitor is the 420 V DC, 2200 µF electrolytic bus capacitor on the outdoor inverter PCB, smoothing the rectified DC that the inverter chops back into the variable-frequency supply driving the compressor. As it ages it loses capacitance and its ESR climbs, so the DC bus ripples — the inverter reads the disturbance and shuts down on a voltage or current fault, often intermittently before it fails outright. Because the bus capacitor and the inverter PCB it serves are renewed together, ordering the genuine electronic part rated for this bus avoids the mismatch a generic capacitor brings — the exact voltage and ripple-current spec Daikin specified.