Genuine Daikin 155291J Outdoor High Pressure Switch is the safety switch that trips if refrigerant pressure on the high side climbs too far, shutting the outdoor unit down to protect it. When it fails, the outdoor unit may shut down for no clear reason, or fail to stop when it should. A genuine switch trips at the pressure your Daikin is set for, keeping that protection reliable — where a non-genuine part can trip early, late, or not at all.