Microwave stops heating and displays F3; may appear immediately after pressing START or during cooking.

Safety warning: Unplug the microwave. Do not remove the outer cabinet or access internal components unless you are a trained technician; high-voltage parts can be lethal.

User-level actions:

• Allow unit to cool: If F3 appeared after heavy use, leave the door open and let the microwave cool for 30–60 minutes, then try again.
• Power reset: Unplug for 10 minutes, then reconnect and test. Sometimes a transient sensor error clears after a reset.
• Check for excessive steam: If you frequently boil liquids or cook high-moisture foods without covering, steam can affect the cavity sensor. Use a microwave-safe cover when cooking to reduce steam exposure.

Technician-level repair (description only): A technician will access the cavity temperature sensor (often mounted on the top or side of the cavity), test its resistance with a multimeter, inspect the wiring harness, and replace the sensor or main PCB if out of specification.

If F3 returns consistently, discontinue use and schedule service; the temperature sensing system is critical for safe operation.