F3
Keystone
Condenser Coil Sensor Calibration / Fault
Keystone air conditioner displays F3 and may not cool properly or may shut down under load.
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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
Aged or damaged condenser thermistor, sensor not in proper location on coil, wiring harness issue, defective main PCB
How to Fix / Troubleshooting
Safety: Unplug the unit and allow hot components to cool.
Steps:
- Locate condenser sensor: Access the outdoor side and find the sensor clipped to the condenser coil or discharge line.
- Verify placement: Ensure it is in firm contact with the metal surface and not hanging loose.
- Inspect wiring: Check for chafing where wires pass through metal. Repair or replace as needed.
- Measure resistance: Compare to expected NTC values. Replace the sensor if out of range.
- Board replacement: If F3 persists with a good sensor and wiring, replace the main control board.
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Repair Difficulty
Hard
4/5
Required Part
Condenser Temperature Sensor
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