F5
Carrier
Defrost Sensor / Outdoor Coil Low-Temperature Fault
Indoor unit displays F5 and system may shut down in heating mode
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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
Defective defrost sensor, Sensor not sensing coil correctly due to poor contact, Outdoor coil heavily iced, Control board defrost logic failure
How to Fix / Troubleshooting
Safety: Turn OFF power before working on the outdoor unit.
- Step 1 – Inspect for ice: Check the outdoor coil for heavy frost or ice buildup. If present, turn the system OFF and allow it to thaw naturally.
- Step 2 – Clean coil: After thawing, gently rinse the coil with water to remove dirt that can trap moisture and cause icing.
- Step 3 – Check sensor placement: Locate the defrost sensor on the outdoor coil or tubing. Ensure it is firmly attached and insulated.
- Step 4 – Replace sensor: If F5 persists, replace the defrost/coil sensor with the correct Carrier part.
- Step 5 – Technician service: If icing continues, a technician should check refrigerant charge, airflow, and defrost control operation.
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Repair Difficulty
Medium
3/5
Required Part
Defrost Temperature Sensor
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