Daikin Fan Coil

Daikin Fan Coil Error Code U3

Troubleshooting guide for the Daikin Fan Coil system fault U3.

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What It Means

Check operation not executed or transmission error.

Possible Causes

  • Check operation is not executed.

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

Check operation not executed or transmission error

All Recorded Causes

Check operation is not executed.

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 check operation is not executed.
  3. Measure airflow-related readings that match the symptom, such as temperature split or static pressure, and check whether the next candidate on the list.
  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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