Why Is My Microwave Sparking or Arcing Inside?
Q: I saw sparks inside my microwave while it was running. Is it ruined?
A: Sparks inside a microwave — also called arcing — can be alarming. Sometimes the cause is simple, like metal or foil inside the cavity. Other times, sparking points to internal damage that makes the microwave unsafe to use.
Below are the most common causes of microwave sparking, what you can safely check, and when it’s time to call our friendly technicians in yellow polos.
1. Metal Objects or Foil Inside the Microwave
The most common reason a microwave sparks is metal inside the oven cavity.
Common culprits include:
- Aluminum foil
- Metal utensils or twist ties
- Plates or mugs with metallic trim
- Takeout containers with hidden metal layers
What to do: Stop the microwave immediately, remove the metal once the unit cools, and avoid using metal unless your manufacturer explicitly allows it.
2. Dirty or Damaged Waveguide Cover
The waveguide cover is a small panel on the inside wall of the microwave that protects internal components and directs microwave energy.
When grease or food splatters build up on this cover, they can burn and cause arcing.
Signs of waveguide problems:
- Brown or black burn marks on the cover
- Burning smell during operation
- Sparks coming from the same wall or corner
In some cases, the cover can be cleaned or replaced. If the metal behind it is damaged, replacement of the microwave may be safer.
3. Chipped or Burned Interior Paint
Over time, the protective paint inside the microwave can chip or wear away, exposing bare metal.
Food splatters on exposed metal can cause repeated arcing.
If the interior shows deep pitting, rust, or large burned areas, the microwave is often unsafe to continue using.
4. Incorrect Use of Metal Racks or Supports
Some microwaves include metal racks designed for specific cooking modes or positions.
Using these racks incorrectly — or during standard microwave cooking — can cause arcing.
Always follow the manufacturer’s instructions for rack use.
Is It Safe to Use a Microwave After It Sparks?
Stop and inspect the microwave before using it again.
Sparking may be minor if:
- Metal or foil was inside during use
- The interior walls and waveguide cover are clean and undamaged
If sparking continues with no metal present — or if interior damage is visible — stop using the microwave and schedule service.
When to Call Beacon
Call Beacon Services & Appliances if:
- The waveguide cover is burned, cracked, or missing
- The interior metal is pitted or heavily scorched
- The microwave sparks during a test run with only a microwave-safe cup of water
Our friendly technicians in yellow polos can determine whether repair is safe — or if replacement is the smarter option — and we’ll see how Beacon can help.