What It Means
Malfunction of transmission (other system).
Daikin Fan Coil
Daikin Fan Coil Error Code U9
Troubleshooting guide for the Daikin Fan Coil system fault U9.
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Possible Causes
- Transmission error between other indoor and outdoor units Defective electronic expansion valve of other indoor unit Defective indoor unit PCB of other indoor unit.
- Improper connection of transmission wiring between indoor and outdoor unit.
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 transmission (other system)
All Recorded Causes
Transmission error between other indoor and outdoor units Defective electronic expansion valve of other indoor unit Defective indoor unit PCB of other indoor unit Improper connection of transmission wiring between indoor and outdoor unit
Verify Before Replacing Parts
- Confirm the exact Daikin model family and fan coil context before acting on a generic code description.
- Confirm filter condition, blower operation, and coil cleanliness before replacing any controls — start by ruling out whether transmission error between other indoor and outdoor units Defective electronic expansion v….
- Measure airflow-related readings that match the symptom, such as temperature split or static pressure, and check whether improper connection of transmission wiring between indoor and outdoor unit.
- After the correction, run the system long enough to confirm the fan coil fault does not return under normal load.
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