Genuine Daikin 1721836 Capacitor is the compressor-circuit run capacitor that holds the phase shift keeping a single-phase compressor turning smoothly under load. As it weakens the compressor starts hard, runs noisily, or stalls and cuts out on the overload. Because the capacitor and contactor that switch the compressor tend to wear together, fitting both genuine on the one job is the sensible call — and the correct Daikin capacitor keeps the motor on its designed phase angle instead of the approximation a generic part gives.