Daikin C9: the suction air thermistor the room setting depends on

What Does Error C9 Mean?

Daikin places C9 in the sensor division against the suction air thermistor, and describes the fault as an abnormal resistance, which covers a disconnection and a short circuit. That sensor reads the air entering the indoor unit, so it is the value the system treats as room temperature and the basis of every capacity decision it makes. Applies to: Daikin indoor units covered by the SM-TS3 malfunction chart, where the C division covers sensor systems The C division on the Daikin chart groups sensor systems, and the detail code selects which sensor. Where a sensor sits inside a particular indoor unit, and what resistance curve it follows, comes from the service manual for that model. A code alone does not tell a technician which physical part to reach for. Owner-safe checks: Note the unit number shown beside C9 and which room it serves before any power is interrupted. | Compare the temperature the controller displays, if it is still visible, against a separate thermometer near the intake. | Confirm filters and panels are correctly seated, and note whether the fault followed any recent cleaning or service. Qualified technician: Measuring thermistor resistance against the published curve and inspecting the indoor board connectors require the casing to be opened by a qualified technician. | A code accompanied by a burning smell, discoloration, or a protective device operating is a stop condition rather than a sensor question.