F3
Comfortmaker
Outdoor Ambient Temperature Sensor Fault
Display shows F3 and outdoor unit may not start or may short-cycle
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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 sun or non-ambient conditions, Damaged sensor wiring, Faulty outdoor PCB
How to Fix / Troubleshooting
Safety: Turn off power at the outdoor disconnect.
Steps:
- Locate ambient sensor: On Comfortmaker condensers, it is often mounted near the coil inlet or control box, exposed to outdoor air.
- Check mounting: Ensure the sensor is shaded and in free air, not touching hot surfaces or in direct sunlight.
- Inspect wiring: Look for damage or loose connections at the outdoor PCB.
- Test resistance: Disconnect and measure resistance; compare to the thermistor chart. Replace if out of spec.
Note: If sensor is good but F3 persists, the outdoor control board may be defective.
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Repair Difficulty
Medium
3/5
Required Part
Outdoor Ambient Temperature Sensor
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