Microwave not heating? Child lock and demo mode, step by step
If your microwave runs, shows the time and the food stays cold, the cause is often the child lock or demo mode. Turning them off takes a few minutes and costs nothing.
- Most common cause
- child lock or demo mode is on
- Time
- 5–15 minutes
- Repair shop, if nothing helps
- 270–820 zł to replace a part
Never take the cover off your microwave. Inside is a high-voltage capacitor that holds a charge even after you unplug the device. Don’t run the microwave empty for long. Don’t use it if the door or the door seal is damaged. You do all the steps below from the outside only.
Step by step
Check whether the lock is on
Look at the display. A padlock, a key or the word “Lock” means the child lock is on. Then the panel doesn’t respond to buttons, or the microwave won’t start heating.
Turn the lock off
Hold the Stop/Cancel button (or the padlock button) for 3 seconds until you hear a beep. The exact combination depends on the model, so if nothing changes, look in the manual for “lock” or “child safety lock”.
Close the door properly
The microwave won’t start with the door not fully closed. Check that there are no food leftovers on the hinges or the latch, and that the door closes with a clear click.
Check whether demo mode is on
If the display shows “Demo”, or the microwave counts down but it’s cold inside, it may be in demo mode. Look in the manual under “demo mode” and use the combination given there. Often it means holding Start, Stop or 0 for a few seconds.
Check the power and mode settings
Make sure the power isn’t set to 0 and that you haven’t selected only the grill or only the fan (convection). In those modes the microwaves don’t work.
Reset the power
Unplug the microwave for 5 minutes, then plug it back in. The control electronics restart, and a random panel freeze goes away.
Do a water test
Put a cup of water inside (not empty!) and run it for 1 minute. If the water is clearly warm afterwards, the microwaves work. If the time runs down and the water is cold even after you have turned off demo mode, the magnetron or the power circuit may be faulty.
- The time runs down and the water and food stay cold even after you turn off the lock and demo mode.
- You hear loud buzzing, see sparks or smell burning.
- The door is bent, doesn’t close, or the seal is damaged.
- The fuses in your flat trip when you turn it on.
How much does a repair shop charge?
| Diagnosis at a repair shop | 70–160 zł |
| Replacing the door latch or microswitch | 160–410 zł |
| Replacing the fuse or control module | 270–680 zł |
| Replacing the magnetron | 410–820 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?
You can turn off the lock and demo mode yourself, so always start there. But if the magnetron is the problem and your microwave is a basic one that costs less than 400 zł, buying a new one is usually cheaper. More expensive models with a grill and convection are worth repairing. Check it in the calculator.
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Open the calculator →FAQ
My microwave lights up and the plate turns, but it doesn’t heat. What does that mean?
Most often the lock or demo mode is on, or the power is set to zero. If none of that applies, the magnetron or its power supply is usually at fault and you need a repair shop.
How do I turn off the child lock on a microwave?
On most models, hold Stop/Cancel or the padlock button for about 3 seconds. Check the exact combination in your model’s manual.
Can I replace the magnetron myself?
We don’t recommend it. You would have to open the cover and discharge the high-voltage capacitor, which can be life-threatening.