Daikin Fan Coil

Daikin Fan Coil Error Code C9

Troubleshooting guide for the Daikin Fan Coil system fault C9.

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What It Means

Malfunction of suction air thermistor.

Possible Causes

  • Defective thermistor for suction air.
  • Defective indoor unit PCB.
  • Defective connector contact.

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

Malfunction of suction air thermistor

All Recorded Causes

Defective thermistor for suction air Defective indoor unit PCB Defective connector contact

Verify Before Replacing Parts

  1. Confirm the exact Daikin model family and fan coil context before acting on a generic code description.
  2. Confirm filter condition, blower operation, and coil cleanliness before replacing any controls — start by ruling out whether defective thermistor for suction air.
  3. Measure airflow-related readings that match the symptom, such as temperature split or static pressure, and check whether defective indoor unit PCB.
  4. After the correction, run the system long enough to confirm the fan coil fault does not return under normal load.

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