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Microwave Not Working

The part(s) or condition(s) listed below for the symptom Microwave not working are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.

Most Frequent Causes for Microwave not working

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Cause 1Line Fuse

If too much current passes through the microwave circuitry, the line fuse will blow. If the line fuse blows, the microwave won’t start. To determine if the line fuse is at fault, use a multimeter to test it for continuity. If the fuse does not have continuity, replace it. In addition, you should investigate and resolve the problem that caused the fuse to blow. If you don’t resolve the underlying issue, the new fuse will blow too. (Caution: The microwave oven can store thousands of volts of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the line fuse.)

Parts
Cause 2Main Control Board

The main control board might be defective. However, this is rarely the case. Control boards are often misdiagnosed—check all of the more commonly defective parts. If you have determined that all of the other components are working properly,replace the main control board. (Caution: The microwave oven can store thousands of volts of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the main control board.)

Parts
Cause 3Thermal Fuse

The thermal fuse cuts off power to the microwave if the microwave overheats. To determine if the thermal fuse has blown, use a multimeter to test it for continuity. If the fuse does not have continuity, replace it. The thermal fuse cannot be reset—if the fuse is blown, it must be replaced. (Caution: The microwave oven can store thousands of volts of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the thermal fuse.)

Parts
Cause 4Thermoprotector

If the microwave overheats, the thermoprotector trips to cut off voltage to the microwave. To determine if the thermoprotector is at fault, use a multimeter to test it for continuity. If the thermoprotector does not have continuity, and it cannot be reset, replace it.

Parts