F1
Carrier Indoor Ambient Temperature Sensor (Room Thermistor) Fault

Indoor unit displays F1 and runs erratically or not at all

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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 room temperature sensor, Sensor dislodged from intake area, Damaged sensor wiring, Indoor PCB sensor circuit failure

How to Fix / Troubleshooting

Safety: Turn OFF power before removing the front cover.

  • Step 1 – Locate sensor: Remove the front panel and filter. The room sensor is usually near the air intake grille, a small probe or plastic-encased sensor.
  • Step 2 – Check placement: Ensure the sensor is not touching the coil or metal parts and is positioned in the return air stream.
  • Step 3 – Inspect wiring: Follow the sensor wires to the PCB. Look for damage or loose connectors. Reseat the connector.
  • Step 4 – Replace sensor: If F1 persists, replace the room temperature sensor with a Carrier-compatible thermistor. Mount it in the same location.
  • Step 5 – PCB evaluation: If a new sensor does not clear F1, the indoor PCB may be defective and require replacement.
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Repair Difficulty

Medium 3/5

Required Part

Room Temperature Sensor (T2 Thermistor)
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