Genuine Daikin 1953518 Humidity Sensor is the sensor that reads the moisture level of the air, giving the indoor unit the reading it uses to manage humidity. When it begins to fail, the unit may stop controlling humidity well, leave the air feeling damp or dry, or run its humidity feature incorrectly. A genuine sensor reads moisture the way your Daikin expects, keeping that control accurate — where a non-genuine part can read off and leave it running wrong.