Quick Checks
Check the Food
Certain foods with high mineral content (like some vegetables) or those containing metallic elements from seasonings can cause minor sparking. Remove the food and try heating a cup of water to see if the sparking stops.
Inspect the Interior
Look for any obvious debris, food splatters, or loose material stuck to the walls, ceiling, or floor of the microwave. Clean the interior thoroughly with a damp cloth. Even small bits of metal can cause arcing.
Check the Waveguide Cover
The waveguide cover is a small, rectangular piece of mica (or similar material) usually located on the right side wall of the microwave interior. If it's damaged, burned, or greasy, it can cause sparking. Do NOT operate the microwave without a waveguide cover.
Common Causes
Metal Objects Inside
DIYMetal reflects microwaves, causing sparks (arcing) as the energy builds up. This includes metal cookware, foil, utensils, twist ties, and even some decorative plates with metallic trim.
Damaged Waveguide Cover
DIYThe waveguide cover protects the waveguide (the component that feeds microwaves into the oven cavity) from food splatters. When damaged, it allows microwaves to contact the metal oven chassis, causing sparks. Replacement covers are available.
Arcing on the Diode
DIYThe high-voltage diode is responsible for providing the high voltage to power the magnetron. Sometimes, arcing will occur around the terminals of the diode which is generally caused by dust build up. The diode can be cleaned using a dry cloth.
Damaged Magnetron
Call ProThe magnetron is the component that generates the microwaves. If it's failing, it can cause internal arcing and sparking. This is a more serious issue and requires professional diagnosis. Altair Home Solutions has the expertise to diagnose and repair magnetron problems.
Damaged or Corroded Interior
Call ProIf the interior paint or enamel is chipped or corroded, the exposed metal can cause arcing. Consistent sparking will lead to further damage of the cavity. Continuing to operate in this condition can create a fire hazard.
High Voltage Capacitor Issues
Call ProA failing high voltage capacitor can sometimes cause internal sparking or arcing. This component stores a significant electrical charge, so diagnosis and repair should only be performed by a qualified technician.
When to Call a Professional
- If you see visible damage or corrosion inside the microwave.
- If replacing the waveguide cover doesn't solve the sparking issue.
- If you suspect the magnetron is failing (loud humming, burning smell).
- If you are uncomfortable working with electrical appliances.
Safety Warning
Microwaves use high voltage electricity. Never attempt to repair internal components unless you are a qualified technician. Unplug the microwave before any inspection or cleaning. If you suspect a high-voltage capacitor issue, do not attempt to repair it yourself – these components store a dangerous electrical charge even when unplugged.
Estimated Repair Cost
$75-$300 (depending on the needed parts and labor). Sealed system repairs can range from $400-$700, avoiding the cost of full unit replacement.
Frequently Asked Questions
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