Genuine Daikin 1786415 Outdoor Four-Way Valve Body is the reversing valve body in the outdoor unit that switches the system between heating and cooling by changing the direction of refrigerant flow. When it sticks or fails, the unit may be stuck in heating or cooling, struggle to change mode, or lose output. A genuine valve body switches the way your Daikin expects, holding reliable mode changes — where a non-genuine part can stick or leak between modes.