F3
Carrier
Outdoor Ambient Temperature Sensor Fault
Indoor unit displays F3 and outdoor unit may not operate correctly 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
Failed outdoor ambient thermistor, Sensor exposed to direct sunlight or heat source, Damaged sensor wiring, Outdoor PCB sensor circuit failure
How to Fix / Troubleshooting
Safety: Turn OFF power at the outdoor disconnect before opening the condenser panel.
- Step 1 – Locate sensor: On the outdoor unit, find the small thermistor usually mounted near the coil or on the control panel bracket.
- Step 2 – Check mounting: Ensure the sensor is not hanging loose or touching hot discharge lines. It should be in free air, shaded by the unit.
- Step 3 – Inspect wiring: Look for UV damage, cuts, or rodent-chewed wires. Reseat the connector on the outdoor PCB.
- Step 4 – Replace sensor: If F3 persists, replace the outdoor ambient temperature sensor with a Carrier-approved part.
- Step 5 – PCB diagnosis: If a new sensor does not resolve F3, the outdoor PCB may be defective and should be replaced by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Outdoor Ambient Temperature Sensor
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