Microwave Problems: Not Heating or Smelling of Burnt Food

A microwave is a kitchen essential that you rely on for quick and easy meals. So when you put a plate of leftovers inside, press “start,” and the food comes out cold, it’s a major frustration. Even more concerning is when your microwave works but produces a terrible, burning smell. These two issues are common but can signal very different problems, some of which can be a safety hazard.

At Star Appliance Repair, we understand the importance of a working microwave. We offer reliable, in-home microwave repair in Toronto  and throughout the Greater Toronto Area (GTA).¹ We’re here to help you get your microwave running safely and efficiently again.

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Part 1: The Microwave Runs, But Doesn’t Heat

If your microwave display lights up, the turntable spins, and you hear the normal humming sound but your food remains cold, the problem is most likely with the internal components responsible for generating the microwaves.²

• Failed Magnetron: This is the most common cause.³ The magnetron is a vacuum tube that creates the high-powered radio waves (microwaves) that heat food.⁴ If the magnetron is faulty or has burned out, the microwave will still power on, but it won’t produce the energy needed to cook.⁵
• A Broken High-Voltage Diode: This component works with the magnetron to generate the high voltage needed for heating.⁶ A defective diode can prevent the magnetron from receiving power, causing the microwave to fail to heat.⁷
• Faulty Door Switch: As a critical safety feature, your microwave has several door switches that prevent it from operating unless the door is completely and securely closed.⁸ If one of these switches is broken, it may not register that the door is shut, so the microwave will power on but won’t begin the heating cycle.⁹
• Blown Thermal Fuse: A thermal fuse is a safety component that will blow if the microwave overheats.¹⁰This can happen due to a blocked vent or a faulty part. Once the thermal fuse is blown, the microwave will not operate until it is replaced.

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Part 2: The Dreaded Burning Smell

A burning smell coming from your microwave is a serious warning sign.¹¹ It’s crucial to unplug the appliance immediately to prevent a potential fire.¹²

• Burnt Food Debris: The most common cause of a burning smell is also the simplest to fix.¹³ Leftover food splatters on the inside walls or ceiling of the microwave can burn and smoke during a new cycle.¹⁴ If this is the case, a thorough cleaning is all that’s needed.
• Melted or Damaged Items: Accidentally putting a non-microwave-safe container, plastic bag, or a piece of foil inside can cause melting, sparking, and a strong chemical or burning odor.¹⁵ Always use microwave-safe dishes and never use metal.
• Failing Internal Components: If the smell persists after cleaning, it’s a sign that an internal component is overheating.
  • A Faulty Magnetron: As mentioned above, a failing magnetron can overheat, producing a strong burning smell.Bad High-Voltage Transformer: This component converts power to the high voltage needed for the magnetron.¹⁸ If it’s failing or has a short, it can cause a burning smell.
  • Malfunctioning Motor or Fan: The cooling fan is essential for preventing the microwave from overheating⁹ If the fan bearing is worn out, it can create a burning smell as it rubs against the shaft.

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DIY vs. Professional Microwave Repair

Microwaves contain extremely high-voltage components, especially the capacitor, which can hold a lethal electrical charge even after the unit has been unplugged.²¹ For this reason, all internal repairs should be left to a trained professional.

What you can do safely:

• Check for simple fixes like a tripped circuit breaker.
• Thoroughly clean the inside of the microwave, paying special attention to the ceiling and the area around the waveguide cover (the small plate inside).²²
• Ensure you are using microwave-safe cookware.

When to call a professional:

• If the microwave is running but not heating, as the issue is almost certainly a complex internal component.
• If you smell burning, especially if the smell is not due to a food spill.²³ This is a safety hazard that requires a professional to diagnose and fix.
• If you see sparks or hear a loud buzzing or grinding sound.

If you’re facing a microwave that won’t heat or is giving off a burning smell, don’t take any chances. A professional can quickly and safely diagnose the problem and get your appliance back in working order.

Don’t hesitate to contact us or call us at (647)-847-8774. We’re here to get your dryer working again in no time.