Daikin error code C9
What it means
Faulty indoor suction air (room) temperature sensor.
Possible causes
Room thermistor failure Poor contact at PCB input Sensor drift outside calibration range
Suggested fix
Check connector integrity and wiring, then compare sensor resistance to Daikin's reference values; replace the thermistor if the readings do not match the expected curve.
Safety first. Isolate the power supply before inspecting any unit. Refrigerant-circuit
and electrical repairs must be carried out by a qualified, registered technician.
Other Daikin codes
- A1 — Indoor PCB defect or internal failure.
- A5 — Freeze-up protection activated for the indoor heat exchanger.
- A6 — Indoor fan motor fault.
- C4 — Faulty indoor heat exchanger temperature sensor.
- E1 — Outdoor circuit board fault.
- E7 — Outdoor DC fan motor fault.
- F6 — High pressure control activated in cooling mode.
- U0 — Refrigerant shortage or undercharge detected.
- U2 — Power supply voltage drop or main circuit overvoltage.
- U4 — Transmission failure between indoor and outdoor units.