Daikin Chiller

Daikin Chiller Error Code C5

Troubleshooting guide for the Daikin Chiller system fault C5.

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What It Means

Reports an open, shorted, or out-of-range reading from the gas-side (suction/discharge gas) thermistor mounted on the indoor or heat-exchanger unit's refrigerant circuit, which the control uses for capacity and freeze-protection calculations.

Possible Causes

  • Thermistor lead pinched, chafed, or corroded at the connector.
  • Thermistor bead not making proper contact with the pipe (poor thermal strapping).
  • Thermistor resistance drifted out of tolerance.
  • Moisture intrusion at the connector.
  • Damaged indoor/heat-exchanger unit PCB thermistor input.

Not sure which one it is — or if it's none of these? Try ACLogics today.

Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
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Full Diagnosis

Reports an open, shorted, or out-of-range reading from the gas-side (suction/discharge gas) thermistor mounted on the indoor or heat-exchanger unit's refrigerant circuit, which the control uses for capacity and freeze-protection calculations. It is the gas-side counterpart to C4 (liquid pipe thermistor) — the two monitor opposite ends of the same heat exchanger circuit and should be checked together when a heat-exchanger thermistor fault appears. It differs from J9, which reports the equivalent gas pipe thermistor fault on the outdoor/compressor-side refrigerant circuit rather than the indoor heat exchanger.

All Recorded Causes

Thermistor lead pinched, chafed, or corroded at the connector. Thermistor bead not making proper contact with the pipe (poor thermal strapping). Thermistor resistance drifted out of tolerance. Moisture intrusion at the connector. Damaged indoor/heat-exchanger unit PCB thermistor input. Wrong thermistor part installed during a prior repair.

Verify Before Replacing Parts

  1. Confirm the exact Daikin model family and chiller context before acting on a generic code description.
  2. Verify airflow first, then confirm operating pressures and temperature relationship before adjusting charge, since thermistor lead pinched, chafed, or corroded at the connector.
  3. Look for restrictions, iced coils, or dirty heat-transfer surfaces that can mimic a charge problem, and separately confirm thermistor bead not making proper contact with the pipe (poor thermal strapping).
  4. After the correction, run the system long enough to confirm the chiller fault does not return under normal load.

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