If your microwave is not working, start with the line fuse, which can blow when excessive current passes through the circuitry and prevent the microwave from starting. Test the fuse for continuity and investigate what caused it to fail, or a replacement may blow again. Next, inspect the microwave switch holder behind the control panel. A damaged or misaligned holder may keep the door switches from actuating when the door closes. If those parts test good, the main control board could be defective, although it is less common and often misdiagnosed. A tripped or failed thermostat can also stop power from reaching the high-voltage components, while an unpowered outlet, tripped breaker, or blown home fuse may cause a microwave not working but has power symptom. Finally, check the thermal fuse, which opens if the microwave overheats and must be replaced if it lacks continuity. Any repair that requires opening the outer cabinet has serious shock risk because the high-voltage capacitor can store lethal charge even after unplugging. Proper capacitor discharge is required, so use a qualified technician if you are not familiar with the procedure. Enter your model number to find the exact replacement part for your microwave.
01 - Microwave Line 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, i...t is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the line fuse.)
Enter model number to search for the required part specific to your product
The microwave switch holder is the component that houses the door switches behind the control panel. If the switch holder is damaged or misaligned, one of more switches may not be actuated when the microwave door is closed, resulting in the microwave not working. You will need to uninstall the control panel and inspect the switch holder to confirm it is in good condition and secured properly. Replace the switch holder with a new one if necessary.
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.)
If the microwave overheats, the thermostat trips to cut off voltage to the microwave. If the thermostat is shorted open, it may not allow voltage to reach the high voltage components. To determine if the thermostat is at fault, use a multimeter to test it for electrical continuity. If the thermostat does not have continuity, and it cannot be reset, replace it.
The electrical outlet may not be getting power. To determine if the outlet is getting power, try plugging something else into the outlet. If the outlet is not getting power, check the home circuit breakers or fuses.
Highly Likely
06 - Microwave Thermal 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.)
Since the control board controls the voltage being sent to all of the microwave's components, a defective board could be responsible for a microwave not working. 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 control board.