Microwave displays F3 and may stop cooking; sometimes appears shortly after starting a cook cycle.

Safety: Disconnect power before accessing internal components. High-voltage parts can be lethal.

• Power reset: Unplug for 5 minutes, then plug back in and test. If F3 returns quickly, proceed with inspection.
• Locate the temperature sensor: On many Kenmore over-the-range microwaves, the cavity sensor is a small metal probe or thermistor mounted inside the oven cavity or behind an interior panel.
• Inspect wiring: With power off, remove the outer cover or interior panel as needed. Check the sensor wiring harness for burns, breaks, or loose connectors. Reseat any loose plugs.
• Basic resistance check (for trained users): Using a multimeter, measure resistance across the sensor leads. Compare to the service manual spec (commonly around 100KΩ at room temperature for some thermistors). If reading is open, shorted, or far out of range, replace the sensor.
• Replace sensor: If wiring is intact but F3 persists and the sensor tests bad, install a new cavity temperature sensor/thermistor compatible with your Kenmore model.

If you cannot safely remove panels or test components, contact a technician. Do not operate the microwave with a suspected sensor fault.