Sharp Microwave Sparking Inside — How to Fix It

What Does This Error Mean?

Sparking in a Sharp microwave is almost always caused by a damaged waveguide cover (the cardboard-like panel on the inside wall) or food debris arcing inside the cavity. Stop immediately and do not use the microwave until the cover is replaced.

Affected Models

Sharp Carousel Microwave
Sharp R-Series Microwave
Sharp Over-the-Range Microwave
Sharp Countertop Microwave

Common Causes

Damaged or burnt waveguide cover (mica sheet on the cavity wall)
Food splatter or grease on the waveguide cover arcing
Metal object inside the microwave (foil, metal trim on dishes)
Damaged interior cavity paint or coating exposing bare metal

How to Fix It

Stop the microwave immediately.

Press Stop or open the door. Continued sparking can damage the magnetron and burn through the cavity walls. Do not ignore sparking.
Inspect the waveguide cover.

The waveguide cover is the cream or brown rectangular panel on one interior wall of the cavity. Look for burn marks, holes, or a blackened area. Even a small burnt spot will cause recurring sparking.
Replace the waveguide cover.

Waveguide covers are made from mica and are inexpensive ($5–$15). Search your Sharp microwave model number for the correct replacement. Remove the old cover (usually held by clips or a tab), wipe the wall clean, and fit the new cover.
Clean the interior cavity thoroughly.

Use a damp cloth to remove all food residue and grease from the cavity walls, ceiling, and turntable. Even small food deposits can cause sparking — especially sugary or fatty residue.

When to Call a Professional

If sparking continues after replacing the waveguide cover and thoroughly cleaning the cavity, the cavity coating or magnetron may be damaged — have a technician inspect it.