Microwave Running Without Heating Food? Here’s Why

If your microwave is running without heating food, there is likely something wrong with one or more of the internal components within your appliance. To help you get to the bottom of the cause of the problem, we have put together this extensive guide.

Hopefully, the issue is easy to remedy, like changing the power settings or adjusting the turntable. But if not, you might have to test internal components. This should only be done by someone experienced in working with microwaves due to the risk of electric shock. If you don’t have any experience working with microwave components, you should book an expert technician to inspect your appliance if the problem isn’t fixed after the first two steps in this guide.

Step 1 – Check the power settings

The most straightforward fix is to check that the power settings are correct. All you need to do is ensure you have your microwave power settings correctly for what you are cooking. For most food items, you should have your microwave set to high.

Step 2 – Adjust the turntable

If the power settings are set correctly, the next step is to ensure the plate in your microwave sits on the turntable in the correct position and that the turntable underneath the plate is securely in place.

Step 3 – Test the door switches

If the power settings and turntable are set up correctly, you must check some of the internal components, starting with the door switches. The switches ensure the door is closed before the microwave can turn on. If any of the switches are defective, your microwave might work but not heat properly. If you don’t have experience working with microwaves and if you don’t have a multimeter, you will need to book a technician to come and inspect your appliance.

Follow these instructions to test the door switches:

1. Open the microwave door and make sure the light inside the microwave turns on. You can then close the door and check if the light goes out. If not, this indicates the door switches are faulty and must be replaced.

2. To double-check the door switches, you can test them with a multimeter for continuity.

3. To test the door switches, switch the power off, locate each switch, and then use your multimeter to do a continuity test of each one. If any of the switches fail the test, replace them. If they all pass the test, move on to the next step.

4. Once replaced, turn your microwave on and check that the food is heating. If the issue isn’t resolved, proceed to the next step.

Step 4 – Check the high-voltage diode

The high-voltage diode converts the A/C power supply into D/C so the magnetron can work correctly. If the diode fails, the magnetron will also fail, resulting in your microwave running without heating the food.

Follow these instructions to test the high-voltage diode:

1. Unplug your microwave.

2. Remove the cabinet (the top and side panels) from your appliance.

3. Locate the diode.

4. Test the diode with a multimeter. If the diode works correctly, the test will show a higher residence on one end than the other.

5. If the diode fails the test, it must be replaced. You can move on to the next step if it passes the test.

6. Once replaced, turn your microwave on and check that the food is heating. If the issue isn’t resolved, proceed to the next step.

Step 5 – Test the magnetron

The magnetron generates the radiation that heats your food. If the magnetron stops working correctly, your microwave will fail to operate. The magnetron must be tested with a multimeter to determine if it is defective.

Follow these instructions to test the magnetron:

1. Unplug your microwave.

2. Remove the cabinet (the top and side panels) from your appliance.

3. Locate the magnetron.

4. Test the magnetron with a multimeter. If the magnetron is working correctly, the test will show 2-3 ohms resistance.

5. If the magnetron fails the test, it must be replaced. You can move on to the next step if it passes the test.

6. Once replaced, turn your microwave on and check that the food is heating. If the issue isn’t resolved, proceed to the next step.

Step 6 – Test the thermal fuse

The thermal fuse switches your microwave off when it overheats. However, sometimes this can happen when it shouldn’t. This is due to the thermal fuse becoming defective.

Follow these instructions to test the thermal fuse:

1. Unplug your microwave.

2. Remove the cabinet (the top and side panels) from your appliance.

3. Locate the thermal fuse.

4. Test the thermal fuse with a multimeter for continuity.

5. If the thermal fuse fails the test, it must be replaced. You can move on to the next step if it passes the test.

6. Once replaced, turn your microwave on and check that the food is heating. If the issue isn’t resolved, proceed to the next step.

Step 7 – Install a new control board

The final step is to install a new control board. Repairing your existing control board is difficult, so your best bet is to install a new one. You could also consider booking a technician to inspect your appliance for a second opinion.