You’re just about to stream your favorite movie, but first you set the package of microwave popcorn on the microwave’s glass turntable. You press the “Popcorn” button and… nothing. Or, you just want to heat up last night’s leftovers for a quick lunch, but you end up eating the lasagna cold. The microwave oven seemed to be operating fine a few days ago, so why is the microwave not working now?
Why Did My Microwave Stop Working? Common Causes Explained
Microwave ovens have become indispensable in modern kitchens, offering quick and convenient meal preparation. However, when your microwave just stopped working, it can be both perplexing and disruptive. Understanding the potential causes of such malfunctions is crucial for effective troubleshooting.
One of the most prevalent reasons for a microwave’s failure is a blown main fuse. This safety device interrupts the flow of electricity when excessive current passes through, preventing potential hazards. Additionally, microwaves are equipped with other protective components like thermal fuses, cavity fuses, and thermoprotectors. These elements are designed to halt electrical flow if the appliance overheats, safeguarding both the device and the user.
Another common culprit is a defective door switch. Microwaves typically have multiple door switches that ensure the appliance operates only when the door is securely closed. If any of these switches malfunction, the microwave may fail to start or heat food properly.
Internal components can also be at fault. For instance, a burned-out diode can prevent the magnetron from receiving sufficient voltage, leading to heating issues. Similarly, a malfunctioning magnetron, the component responsible for generating microwave radiation, can result in the appliance not heating food as expected.
It’s also worth noting that issues like a faulty high-voltage capacitor or a failed high-voltage transformer can disrupt the microwave’s operation.
Recognizing these potential problems is the first step toward resolving them. In the following sections, we’ll delve deeper into these common causes of microwave malfunctions and provide practical solutions to help restore your appliance’s functionality.
How to check a fuse if your microwave is not working
The most common cause for a microwave oven not working at all is a blown main fuse. The microwave main fuse will cut the flow of electricity if too much current passes through it. When this happens, the fuse is considered “blown” and the microwave’s fuse will need to be replaced with a new one before the microwave will start working again. The main fuse is not the only fuse found in microwave ovens. There can also be microwave thermal fuses, cavity fuses, and microwave thermoprotectors, which will interrupt the electrical flow if the microwave overheats. All of these parts can be tested with a multimeter to confirm continuity – a continuous electrical path present in the component. Here are some troubleshooting tips if your microwave suddenly stops working:
- Before you begin testing, unplug the microwave oven power cord.
- Since high-voltage capacitors used in microwaves may retain a charge even after the power cord has been unplugged, it is recommended to discharge the microwave’s capacitor before servicing. You can do this by placing a screwdriver blade across each set of capacitor terminals (avoid touching the blade when doing this).
- Remove the fuse or thermoprotector from the appliance.
- Rotate the multimeter dial to the lowest setting for “Ohms of resistance”.
- Touch the black lead to one of the component’s terminals and the red lead to the other terminal.
- If the meter display shows zero Ohms of resistance, the component has electrical continuity; if the meter display shows no significant change, the component lacks continuity, which means it has blown and will need to be replaced.
Keep in mind that a blown fuse is often caused by a faulty microwave door switch.
A faulty door switch can prevent the microwave from working
Most microwaves have three or four door switches that allow the appliance to start or heat once the door is fully closed. A faulty door switch will prevent the microwave from working even after the door has been closed. As with the fuses and thermoprotector, you can test each door switch for continuity to determine if one has failed:
- Two-terminal door switches will either have continuity before the switch is actuated or after; three-terminal door switches will have a “common” terminal, a “normally closed” terminal that provides continuity before the switch is actuated, and a “normally open” terminal that provides continuity after the switch is actuated.
- For two-terminal switches, touch the black lead to one terminal and the red lead to the other terminal, then actuate the switch. If the meter display shows zero Ohms of resistance, the switch has continuity; if the meter display shows no significant change, the switch has no continuity and is faulty.
- For three-terminal switches, touch the black lead to the “common” terminal and the red lead to the “normally closed” terminal. The multimeter display should show zero Ohms of resistance. Move the red lead to the “normally open” terminal, and the multimeter should indicate continuity only after the switch has been actuated.
- Be aware, if either a two-terminal or three-terminal door switch tests positive for continuity when it should not, it is likely the switch has shorted closed.
Could the main microwave control board be defective?
Although it’s not a common cause, a defective main control board could prevent the microwave from working as well. Since it’s difficult to test a microwave’s control board accurately, you should confirm that the fuses, thermoprotector, and door switches all have electrical continuity and are functioning normally before you consider replacing the board.
Other Reasons Why Your Microwave Stopped Working Suddenly
While common culprits like blown fuses, defective door switches, or faulty control boards often take the blame, there are several other potential reasons why your microwave may have suddenly stopped functioning. Here are a few less commonly discussed factors:
1. Microwave Switch Holder
The microwave switch holder is a crucial component that ensures the door switches are properly engaged when the microwave door is closed. If the switch holder is damaged, misaligned, or broken, it may fail to activate the door switches, preventing the microwave from starting. This issue can sometimes be resolved by adjusting the holder or replacing it if necessary.
2. Microwave Thermostat
The microwave thermostat acts as a safety mechanism that monitors the internal temperature. If it detects excessive heat, it may trip and cut off power to key components like the magnetron or transformer. A defective thermostat can mistakenly prevent the microwave from running, even when there is no overheating issue. Testing the thermostat with a multimeter and replacing it if necessary can help restore functionality.
3. Microwave Thermoprotector
Similar to the thermostat, the microwave thermoprotector is another safety device designed to shut off power if the microwave overheats. However, unlike a resettable thermostat, a tripped thermoprotector often requires replacement. If the microwave suddenly stops working and won’t turn on, checking the thermoprotector for continuity may help determine if it needs to be replaced.
4. Incoming Power Problem
A microwave may fail to start due to issues with the power source rather than the microwave itself. Possible causes include:
- A tripped circuit breaker that needs to be reset.
- A faulty wall outlet that isn’t supplying power.
- A loose or damaged power cord that interrupts electricity flow.
Testing the outlet with another appliance or plugging the microwave into a different outlet can help diagnose power-related issues.
5. Microwave Thermal Fuse
While many articles focus on the main line fuse, the microwave thermal fuse is another critical component that may be overlooked. This fuse is designed to cut off power when the microwave overheats, protecting it from further damage. If the thermal fuse blows, the microwave will not turn on until the fuse is replaced. Checking the thermal fuse with a multimeter for continuity is essential if the microwave is completely unresponsive.
6. Microwave Flywheel Key
Though not a common failure point, some older or specialized microwave models utilize a flywheel or mechanical engagement system to operate internal components. If the flywheel key becomes damaged or misaligned, the microwave may fail to function correctly. Inspecting the flywheel and its associated parts can help determine if this is the cause of the problem.
By considering these additional factors, you may be able to diagnose and fix your microwave issues more effectively. If troubleshooting doesn’t resolve the problem, it’s best to consult a professional technician to avoid potential electrical hazards.
Microwave Safety Warning
Because of the high voltage and high current used by microwave ovens, be aware that repairing this appliance poses a substantial risk of injury or death if precautions are not taken. You should always unplug the microwave before taking apart a microwave. Since high voltage capacitors used in microwaves may retain a charge even after the microwave has been unplugged, we recommend that only experienced professionals access and replace internal components.
Top Reasons your Microwave Is Not Working – Microwave Oven Troubleshooting
Does your Microwave Start then Stop after a few seconds?
If your microwave starts and then stops after a few seconds, it could be due to a faulty door switch, control board, or high-voltage transformer. For detailed troubleshooting steps and part replacement guides, visit our Microwave Shuts Off After a Few Seconds Repair Help Page. Repair Clinic offers expert guidance and quality replacement parts for all major brands like GE, Whirlpool, Samsung, LG, and more.
Find the right microwave oven parts with Repair Clinic
Repair Clinic stocks all the replacement appliance parts that match your microwave oven, including fuses, door switches, and main control boards. Enter the full model number of your microwave in the Repair Clinic website search bar to see a complete list of compatible parts, such as Whirlpool parts for a Whirlpool microwave, then use the part category and part title filters to narrow the list down to identify the exact part you need. While Repair Clinic carries parts that fit microwaves from top brands like GE, Samsung, Whirlpool, LG, Kenmore, Frigidaire, and Panasonic, you’ll want to make sure you’re selecting a part that is directly associated with your specific microwave oven model. If your microwave is not working now, hopefully, our tips can help you get it back up and running again.