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.
Microwave Turntable Not Turning? Microwave Oven Troubleshooting
Microwave Not Working? Microwave Oven Troubleshooting
Microwave Not Heating? Microwave Oven Troubleshooting
Microwave Light Bulb Not Working? Microwave Oven Troubleshooting
Microwave Is Loud/Noisy? Microwave Oven Troubleshooting
Microwave Exhaust Fan Not Working? Microwave Oven Troubleshooting
Microwave Buttons Not Working? Microwave Oven Troubleshooting
Removing Microwave Trim - Tech Tips from Repair Clinic
Replace Microwave Charcoal Filter - Tech Tips from Repair Clinic
Boil Water in Your Microwave - Tech Tips from Repair Clinic
5 Tips For Your Microwave - Tech Tips from Repair Clinic
Microwave Sparking/Arcing? Microwave Troubleshooting
Microwave Door Won't Open? Microwave Troubleshooting
Microwave Turns On By Itself? Microwave Troubleshooting
Microwave Display Not Working? Microwave Troubleshooting
Microwave Shuts Off After A Few Seconds? Microwave Troubleshooting
What Causes a Microwave to Spark and Arc?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.)
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.
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.
The diode converts the A/C power output of the transformer to D/C, doubling the voltage to nearly 5,000 volts. This high voltage powers the magnetron to heat the food. If the diode burns out, the magnetron won’t receive enough voltage to operate, preventing the microwave from working. When the diode fails, it is often visibly burned out. Inspect the diode and if the diode is burned out, replace it. If inspecting the diode proves inconclusive, test it with a multimeter that uses a 9-volt battery or put a 9-volt battery in series with the diode. When the leads are reversed, the diode should only have continuity in one direction. (Warning: The microwave oven can store a lethal amount of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the high running voltage and the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the diode.)
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.
After a power surge or power outage, appliance operation could be temporarily affected. Full operation can sometimes be restored through a power reset by either unplugging the unit's power cord for a few seconds and then plugging it back in or switching off the circuit breaker for the microwave then switching it back on.
If the microwave overheats, the high limit thermostat will trip to cut off voltage to the microwave. If the thermostat is shorted open, it may not allow voltage to reach the high voltage components which will prevent the microwave from working. 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.
Most microwaves have three or four door switches. When the microwave door closes, the door switches actuate in sequence to ensure that the door is closed properly. If any of the door switches fail, the microwave will not start or heat. To determine if any of the door switches are defective, use a multimeter to test each of the switches for continuity. If any of the door switches do not have continuity, the switch or switches should be replaced.
Most microwaves have three or four door switches (micro switches). When the microwave door closes, the door switches actuate in sequence to ensure that the door is closed properly. If any of the door switches fail, the microwave will not start or heat. To determine if any of the door switches are defective, use a multimeter to test each of the switches for continuity. If any of the door switches do not have continuity, the switch or switches should be replaced.
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.
