Daikin error code C4
What it means
Faulty indoor heat exchanger temperature sensor.
Possible causes
Heat exchanger thermistor open or short Connector not fully seated Sensor harness damage
Suggested fix
Measure thermistor resistance and inspect harness and connector condition; renew the sensor or repair the wiring, and clear the code after confirming stable readings within specification.
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.
- C9 — Faulty indoor suction air (room) 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.