Microwave causes visible sparks or arcing inside the cavity

Immediate safety action: Press STOP and unplug the microwave. Do not continue to run it while arcing occurs.

Step-by-step checks:

• 1. Remove metal: Ensure there are no metal utensils, foil, or containers with metallic trim inside.
• 2. Inspect waveguide cover: Check the mica waveguide cover for burn marks, holes, or heavy grease. Replace if damaged; clean gently if only lightly soiled.
• 3. Check cavity paint: Look for chipped or worn paint exposing bare metal, especially on the cavity walls and ceiling. Small chips can sometimes be touched up with microwave-safe cavity paint; extensive damage requires professional evaluation.
• 4. Clean thoroughly: Remove all food splatter and grease, particularly near the waveguide area.
• 5. Test: After corrections, test with a cup of water. If arcing persists, unplug and contact a technician.