Display shows F3; defrost cycle timing appears incorrect, with either too much frost or excessive defrosting.

Safety first: Unplug the refrigerator before accessing the evaporator and sensors.

• Locate defrost thermistor: It is usually clipped to the evaporator tubing near the top or middle of the coil.
• Check placement: Ensure the sensor is firmly clipped to the tubing for accurate temperature sensing.
• Test resistance: Disconnect and measure resistance at a known temperature; compare to spec. Replace if out of range.
• Inspect wiring: Look for brittle or broken insulation from repeated freezing and thawing.
• Replace sensor: Install a new thermistor if needed, reclip securely, and restore power.