Daikin Split & Multi-Split Error Code C5

Full Diagnosis

C5 indicates the indoor unit's gas-side (suction/discharge) heat exchanger thermistor has failed open, shorted, or is reading out of range, so the PCB can no longer track refrigerant gas pipe temperature for coil freeze protection and capacity control. The unit shuts down on the affected indoor coil only; on a multi-split, the outdoor unit and other zones continue operating unaffected. C5 is the gas-line counterpart to C4, which covers the same heat exchanger's liquid-side thermistor — the two are diagnosed and replaced independently even though they sit on the same coil.

All Recorded Causes

Gas pipe thermistor open or shorted internally. Thermistor bulb dislodged from its clamp and no longer in contact with the pipe. Corroded, loose, or oxidized connector pins at the indoor PCB. Wiring harness chafed or pinched between the coil and PCB. Moisture intrusion at the thermistor connector. Defective indoor unit PCB thermistor input circuit.

Verify Before Replacing Parts

1. Confirm the exact Daikin model family and split/ multi split context before acting on a generic code description.
2. Verify airflow first, then confirm operating pressures and temperature relationship before adjusting charge, since gas pipe thermistor open or shorted internally.
3. Look for restrictions, iced coils, or dirty heat-transfer surfaces that can mimic a charge problem, and separately confirm thermistor bulb dislodged from its clamp and no longer in contact with the pipe.
4. After the correction, run the system long enough to confirm the split/ multi split fault does not return under normal load.