Microwave shows F3 and will not start or stops mid-cycle; may be accompanied by erratic temperature sensing in convection models.

Safety First: Unplug the microwave or turn off the breaker. Do not work near the high-voltage section.

• Locate the sensor: On JennAir over-the-range and built-in convection microwaves, the temperature sensor or thermistor is usually mounted on the rear or side wall of the oven cavity, often behind a small cover.
• Visual inspection: Check the sensor and its wiring for burns, broken insulation, or loose connectors.
• Test resistance: With power disconnected, remove the sensor connector from the harness. Use a multimeter to measure resistance. Typical oven sensors are around 1000–1100 Ω at room temperature (consult your model’s tech sheet for exact values). A reading of 0 Ω (short) or infinite (open) indicates a bad sensor.
• Check harness: If the sensor tests good, inspect the wiring from the sensor to the control board for pinched or broken wires.
• Replace faulty component: Replace the oven temperature sensor or cavity thermistor if readings are out of range. If sensor and wiring are good, the electronic control board may need replacement.