Genuine Daikin 4011066 Outdoor Thermistor Assembly is the temperature-sensor assembly in the outdoor unit that gives the system the readings it uses to run correctly through the cycle. When it starts to fail, the outdoor unit may struggle to hold output, run hot or cold, or stop and start at odd times. A genuine assembly reads temperature the way your Daikin expects, keeping the system accurate — where a non-genuine part can read off and leave it running incorrectly.