F5
Fujitsu
Indoor Intake Air Temperature Sensor Fault
Indoor unit shows F5, unit may not respond correctly to remote control temperature settings
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Open or shorted intake air thermistor, Sensor out of airflow path, Loose connector on indoor PCB, Failed indoor PCB sensor circuit
How to Fix / Troubleshooting
Safety first: Turn off power at the breaker before removing the indoor front panel.
- Locate intake sensor: This thermistor is usually positioned near the return air grille or behind the filter, sensing room air entering the unit.
- Check placement: Ensure the sensor is not tucked behind insulation or touching the coil; it should be in the airflow.
- Inspect and reseat connector: Follow the sensor wires to the PCB and reseat the connector.
- Resistance measurement: With the sensor unplugged, measure resistance at room temperature and compare to Fujitsu specs. Replace if readings are abnormal.
- Test operation: After replacement, restore power and verify that the unit responds normally to temperature changes and that F5 is cleared.
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Repair Difficulty
Medium
3/5
Required Part
Indoor Intake Air Thermistor
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