Microwave not heating or sparking inside? What you can fix cheaply
Sparking is usually a burnt mica cover that costs a dozen or so złoty. No heating is most often the magnetron or the high-voltage fuse. Only a repair shop should do that repair.
- Most common cause
- mica cover (sparks), magnetron (no heating)
- Time
- 10–15 minutes
- Repair shop
- 200–480 zł (magnetron)
Never open the microwave's casing. Inside is a capacitor that holds a lethal voltage even after you unplug it. Replacing the mica cover inside the cavity is safe, the inside of the casing is not.
Step by step
Test with a glass of water
Put a glass of water in for 1 minute at full power. The water should be clearly warm. If it's cold, the microwave isn't heating.
Check the settings
Make sure you haven't selected defrost mode, low power or grill only.
Remove metal from the cavity
Aluminium foil, cutlery and dishes with gold decoration cause sparks. Take them out before switching on.
Inspect the mica cover
On the side wall of the cavity there's a grey, matte rectangle. It's the mica cover that protects the waveguide. If it's burnt or greasy, replace it. It costs a dozen or so złoty and you can trim it with scissors.
Clean the cavity
Burnt food residue also sparks. Clean the cavity with a bowl of water with vinegar or lemon, heated for 3 minutes.
Check the plate
If the plate doesn't turn, check how the roller ring and the spindle are seated. The plate motor is a cheap part.
- The microwave doesn't heat even though the settings are right.
- It sparks even with a new mica cover and a clean cavity.
- The door doesn't close properly or is bent. Don't use it in that case.
How much does a repair shop charge?
| Mica cover (part) | 10–40 zł |
| Replacing the magnetron | 200–480 zł |
| Replacing the high-voltage fuse / diode | 140–270 zł |
| Plate motor | 70–160 zł |
Typical prices at independent repair shops in Poland, October 2026. Authorised service centres and big cities can be more expensive.
Repair or buy new?
The mica cover always pays off. Replacing the magnetron makes sense in built-in microwaves and pricier models. With cheap freestanding ones (up to 500 zł), buying a new one is usually better.
Check if it's worth repairing your microwave
Pick your model and fault. In 2 minutes we show the repair cost, what the device is worth and an honest verdict.
Open the calculator →FAQ
Is a sparking microwave dangerous?
Sparking can damage the magnetron and the cavity, and in extreme cases set food residue on fire. Switch it off and find the cause.
Can I replace the magnetron myself?
No. It means opening the casing and discharging the high-voltage capacitor. That's a job for a repair shop only.
Why does my microwave heat more weakly than it used to?
The magnetron weakens over time. If heating takes clearly longer than before, it's natural wear.