Why Is My Microwave Sparking and Arcing?

by Rowan Guthrie
Young Man Spraying Fire Extinguisher On Microwave Oven In The Kitchen

Microwave ovens are a vital part of any kitchen, not only because they’re so useful but because they’re so reliable. So when a microwave starts sparking and arcing, it’s unsettling. (It can also disrupt your reheating leftovers for dinner and popcorn movie nights.)

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But before you throw the appliance to the curb, understanding the reasons behind the light show can help you determine the appropriate course of action.

What Are the Possible Causes of Sparking and Arcing in a Microwave?

Microwave ovens generate electromagnetic waves to heat food. When these waves meet anything metallic, they bounce around erratically instead of penetrating your dinner. This erratic bouncing can cause sparks or arcing (a mini-lightning bolt) within the microwave cavity. Here are the usual suspects:

Metal in the Microwave

While modern microwaves are designed to be safe for everyday use, placing metal objects inside can result in sparking and arcing. Metallic items such as aluminum foil, metal utensils and containers with metallic accents can reflect microwaves, causing electrical currents to flow and sparking to occur. Therefore, avoid putting any metal objects inside the microwave, as they can damage the appliance and pose a fire risk.

Food Particles

A common culprit behind microwave sparking is leftover food particles or grease within the appliance. When food debris accumulates on the interior surfaces, especially the walls or ceiling, it can lead to sparking during the cooking process. These particles can absorb microwave energy, become superheated and cause arcing.

Faulty Waveguide Cover

The waveguide cover is a small, rectangular-shaped piece located inside the microwave oven cavity. It protects the magnetron — an essential component that generates microwaves — from food splatters and moisture. If the waveguide cover becomes damaged or dislodged, it can expose the magnetron to food debris or grease, leading to sparking and arcing.

High-Voltage Capacitor or Diode Failure

While less frequent than the previous examples, internal components such as the high-voltage capacitor or diode can malfunction and cause sparking. These repairs are best left to qualified microwave repair technicians.

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Is Microwave Sparking a Fire Risk?

A sporadic spark or two might not be an immediate fire hazard. However, if left unattended or ignored, it can potentially lead to more serious safety hazards. For instance, if food particles continue to accumulate and spark repeatedly, they could ignite and cause a fire. Additionally, if the sparking is due to a malfunctioning component, such as a faulty capacitor, it could result in electrical issues that increase the risk of fire.

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What Should You Do If Your Microwave Is Sparking?

1. Unplug the microwave immediately: Think safety first. Don't open the door or attempt to use the sparking microwave. Disconnect it from the power outlet right away.

2. Identify the culprit: Check for any metal objects inside the microwave. Inspect the cavity for food debris, particularly around the waveguide cover.

3. Clean your microwave: If it's food debris, thoroughly clean the interior with a damp cloth and mild soap. Pay particular attention to the waveguide cover.

4. Evaluate the damage: If the culprit isn't metal or easily cleaned food residue and you suspect a deeper issue, it's time to call in a professional.

DIY or Call a Technician?

Here's when to consider a repair technician:

  • If the sparking persists after cleaning
  • If you suspect damage to the waveguide cover, such as visible signs of cracking and burning
  • If you're unsure about the source of the sparking

Replacing a faulty waveguide cover might be a cost-effective solution if you feel confident enough in your DIY skills and you’re aware of the safety risks and what to do to keep yourself safe. However, diagnosing and repairing internal components, such as the capacitor or diode, is best left to trained professionals. Microwaves contain high-voltage capacitors that can hold a lethal electrical charge even after the appliance is unplugged. Disassembling a microwave for repairs can be dangerous and could also void your warranty. So if you have any doubts at all, call in an expert.

Finally, sparking is a warning sign, not a death sentence for your microwave. By addressing the cause promptly, you can likely get your appliance back in safe working order and enjoy those reheated dinners and popcorn again without any risks.

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