Visible sparks (arcing) inside the microwave cavity during cooking.

Safety first: Immediately press STOP and unplug the microwave if you see sparks.

• Remove offending items: Take out any metal utensils, foil, or containers with metallic trim. Do not use them again in the microwave.
• Clean interior: Thoroughly clean the cavity, especially areas where arcing occurred. Dried food or grease can cause sparks.
• Inspect cavity coating: Look for chipped or peeled paint exposing bare metal. Small areas can sometimes be touched up with microwave-safe cavity paint, following the product instructions.
• Check waveguide cover: Replace the cover if it is burned or damaged.
• Next step: If arcing continues with no metal present and a clean cavity, internal components or the cavity itself may be damaged. Discontinue use and consult a technician.