Fill a microwave-safe cup with water and place it inside the Kenmore. Microwaves should not be operated while empty.
Press the "Cook" button. Enter "60" and press "Start." If the oven has a problem, it will shut down after 10 seconds and begin flashing "F9" on the display panel.
Open the door and close firmly, and then press the "Start" button.
Cut off power to the Kenmore at the circuit breaker. Wait one minute, and then restore electricity to the appliance. This resets the unit.
Test the microwave again by starting the appliance for 60 seconds. If it continues to shut off and display the "F9" error message, the problem may be with the inverter wiring harness inside the unit. Professional repairs are necessary.