Trane air conditioner shows F3 and may stop cooling; outdoor unit may shut down on protection.

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.

Possible Causes

Failed outdoor ambient thermistor, Sensor wire damage from weather or animals, Loose connector at outdoor board, Incorrect sensor resistance

Safety first: Turn off power at the outdoor disconnect before accessing the control compartment.

Locate ambient sensor: The sensor is typically mounted near the outdoor coil or on the control panel, exposed to outdoor air.
Inspect sensor and wires: Check for cracked casing, UV damage, or chewed wires. Repair wiring with weatherproof splices if needed.
Secure connection: Ensure the sensor plug is fully seated on the outdoor control board.

If F3 persists, replace the ambient sensor with the correct Trane thermistor specified for the model.

Medium 3/5

Trane Outdoor Ambient Temperature Sensor

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