Microwave displays F3 and will not start a cooking cycle.

Safety first: Unplug the microwave. High-voltage components inside can be dangerous; avoid contact with the capacitor and magnetron area.

• Locate the temperature sensor: On Fisher & Paykel models with F3, the cavity thermistor is usually mounted on the top or side of the oven cavity behind the interior liner or behind the control panel area.
• Inspect wiring: Check the harness from the thermistor to the control board for pinched, burned, or broken wires. Repair or replace damaged wiring.
• Test thermistor: Disconnect the thermistor and measure its resistance with a multimeter at room temperature. Compare to the specification in the service manual. If it reads open, shorted, or far out of range, replace the thermistor.
• Check connectors: Reseat the thermistor connector at both the sensor and control board ends. Ensure pins are not bent or corroded.
• Replace control board if needed: If the thermistor and wiring test good but F3 remains, the control board's sensor circuit may be defective. Replace the main control PCB with the correct Fisher & Paykel part.