Indoor unit displays F5, often associated with outdoor ambient temperature sensor

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

Open or shorted outdoor ambient thermistor, Sensor dislodged from mounting, Damaged sensor wiring, Faulty outdoor PCB sensor circuit

Safety first: Turn off power at the outdoor disconnect before opening the unit.

Steps:

Locate ambient sensor: Find the thermistor mounted near the outdoor coil or air inlet grille.
Check mounting: Ensure it is properly positioned in free air, not touching hot components.
Inspect wiring: Look for damage or corrosion on the sensor leads.
Measure resistance: Test resistance and compare to the temperature–resistance chart. Replace if out of spec.
PCB diagnosis: If a new sensor does not resolve F5, the outdoor PCB may be defective.

Medium 3/5

Outdoor Ambient Thermistor

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