If your microwave is making a loud humming noise, first check to see if it still heats efficiently. Often, the humming noise is associated with a microwave malfunction. The following tips will help you troubleshoot the problem in either situation.
Microwave still heats:
It is likely that grease or food debris is causing the humming sound. Sometimes grease or food becomes stuck behind the stirrer/waveguide cover and creates the noise. Make sure to clean behind the cover to clear away any debris.
Microwave does not heat:
If the microwave does not heat, the humming is likely caused by a malfunction of one of three parts: the power diode, high voltage capacitor, or magnetron.
1) Power Diode — This is an electronic component that readily passes current in one direction only and blocks the flow of current in the opposing direction. If your microwave’s diode has become defective, then your microwave will not heat and you will hear a buzzing noise. Test the diode to determine if this is the cause of your problem. Replace it if it is defective.
2) High Voltage Capacitor — This device stores electricity. Test the capacitor to determine if this is the cause of your problem. A defective capacitor will have to be replaced before your microwave will work again. Make sure you discharge the capacitor before you test it.
3) Magnetron — This is the device that creates the “microwaves” that heat your food. Test the magnetron and replace if necessary.
Caution: Your microwave oven is capable of giving you a serious electrical shock, even when it is unplugged. We strongly suggest you seek the assistance of an appliance repair technician when conducting any microwave oven repair.
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