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Q: I tried to heat the leftovers and heat the tea in the microwave without success. My microwave doesn’t heat up because it’s broken and can’t be fixed, or is there some way to fix it?
A: It is a disadvantage to lose the ability to reheat food and beverages in a few minutes. Microwaves are a bit of a mystery to most of us, so it’s natural to assume that they will need a replacement the moment they stop working. If the microwave does not heat up, there are several parts that can be responsible for the problem, from the door switches to the magnetrons. With the help of a multimeter, you can solve the three most common problems on your own; be sure to unplug the microwave before inspecting the internal operation. However, if you are unsure of how to approach the problem, it may be best to use the services of a professional to help you diagnose and fix the problem.
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If a microwave does not heat up, there may be a problem with the high voltage diode.
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The diode is the equipment that helps channel and provide electricity in one direction to the magnetron, and is usually located behind the microwave front panel near the controls. If it is burned, the microwave will not generate energy to spin the magnetron and heat the food.
You can remove the front cabinet board with a Phillips head screwdriver (after disconnecting the microwave) and check the polarity of the diode with one of the best multimeters. It should show low resistance in one direction and high resistance in the other. If not, or if it shows continuity at both ends, the high voltage diode needs to be replaced. Sometimes the diode shows a correct polarity and in this case a qualified technician may need to check the general high voltage power circuits in the microwave.
There may be a problem with the door switch: a microwave will not heat up until the door is closed.
From time to time, the door switch of an older microwave may not lock properly, especially when the door closes frequently. It is a good security mechanism, as a microwave would work safely with the door open. A good indicator that the problem with the door switch is that the light stays on when the door is closed and the microwave is not working.
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You can check this problem by unplugging the unit, unloading the outer screws and removing the outer housing from the cabinet, and using a multimeter to check for power through the switches. If your microwave has a button to release the door, press it down while checking the door switches. If the microwave terminals read zero, they have continuity. Otherwise, the switches will need to be replaced.
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The problem may be the magnetron, which generates heat from the microwave.
When a magnetron fails, it can also blow fuses, which can cause other microwave failures. You can check if the magnetron works by unplugging the unit, removing the cabinet housing, discharging the high voltage capacitor safely, and removing the magnetron. With the multimeter, you can check the load from the terminals. They should read 2 to 3 ohms of resistance if the magnetron still works. Then use a probe to touch the metal housing that closes the magnetron; if it reads zero, there is a problem. This step should only be completed once the condenser has been properly discharged using a rubber screwdriver or other safety tool.
It is recommended that a professional replace a defective magnetron due to the dangerous nature of high voltage repairs. You can also leave the diagnosis of the magnetron to a professional if you prefer. Depending on the age of your microwave, it is worth considering replacing the unit completely if the magnetron is turned off.
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Make sure the timer is not set to bake several hours in advance.
As embarrassing as it is, sometimes microwaves don’t work because of our own user error. It’s a good chance that many of us have rarely used the extra function buttons on our microwave, as we usually only need a couple of minutes to save a bag of popcorn or sterilize a cutting board. If the microwave does not heat up, you may want to check if the delay timer is set to start cooking later. You can always turn off the microwave for a moment to reset the system if the timer is not easily canceled.
Make sure you do not heat items that cannot be microwaved.
Microwaves are useful for heating leftovers, heating water and more, but believe it or not, they are not capable of heating certain foods. While cases of making this mistake are uncommon, it’s a good idea to check that you don’t heat very dry or fat-free foods. Although the physics behind the phenomenon is more complex, microwaves essentially heat water and fat molecules in food better than they do not heat other molecules. Therefore, if the food does not heat up fast enough or does not heat up at all, it may be because the food does not contain fat, is very dry or both. Remember that there are certain foods and materials that should never be heated in the microwave for safety reasons. Warming up metals can cause significant damage to the appliance (and even at home) and thawing meat in the microwave can be unsafe due to the growth of bacteria.