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

Safety: Disconnect power at the breaker. Internal components can be sharp and high-voltage parts are dangerous.

• Locate the sensor: On Viking convection or microwave/oven combo units, the temperature sensor is typically mounted on the rear interior wall of the cavity with two screws and a wire harness leading to the control board.
• Visual inspection: Remove the interior mounting screws and gently pull the sensor forward. Check for burned insulation, broken wires, or corrosion at the connector.
• Check connections: Follow the harness to the control board (accessed from the top or rear). Ensure the sensor plug is fully seated on the Viking control board.
• Resistance test (for qualified users with a meter): With the sensor disconnected and at room temperature, measure resistance across the sensor leads. Typical Viking sensors read around 1000–1100 Ω at 70°F (21°C). If reading is open, shorted, or far out of spec, replace the sensor.
• Replace sensor if faulty: Install a new Viking oven temperature sensor, route the harness away from hot or sharp edges, and secure with original screws.
• If sensor tests good: The main control board sensor circuit may be defective and require replacement.