Safety warning: Stop the microwave immediately if you see sparks or flames. Arcing can damage the magnetron and cavity.

Steps to try:

1. Stop and inspect: Open the door (after the magnetron stops) and remove any metal utensils, foil, or dishes with metallic trim.
2. Check waveguide cover: Locate the small rectangular cover (often a mica plate) on the side or top interior wall. If it is burned, cracked, or has holes, it must be replaced.
3. Clean cavity: Gently clean food splatters, especially near the waveguide cover, with a mild detergent and soft cloth. Do not use abrasive pads.
4. Inspect enamel: Look for chipped or bare metal areas. Small chips can sometimes be touched up with microwave-safe cavity paint by a technician.
5. Test with water: After cleaning and removing metal, test with a cup of water. If arcing persists, stop using the microwave.

Waveguide cover replacement and cavity repairs should be done with Siemens-approved parts.

Microwave produces sparks or arcing inside the cavity during cooking.

Possible Causes