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It’s a fairly common problem, but determining why your microwave oven turns on when the door is open isn’t too complicated if you’re careful. It can be an easy fix, or the malfunction could be a sign of a problem that will require a professional repair or entire replacement- in which case you might want to take a look at the best microwaves now available.
With a few basic steps, you can isolate the issue and hopefully get your microwave working properly again. You can also find out here about DIY repairs and troubleshooting steps for microwaves like how to fix rust on a microwave. Even questions like why plates get too hot in your microwave have fairly easy-to-understand answers.
Testing door interlock switches using a multimeter generally isn’t necessary since 90% of issues with microwaves running with an open door are due to fault interlock switches.
9 times out of 10, a microwave that continues to run when the door is open has an issue with a device called the door interlock switch which runs a signal from the door to the electrical components. First, check that it’s not running with the door closed as well even when you press stop- if it’s running in both states, you more likely have a problem with the control board.
Once you’ve made sure the issue is only with the open door, you can use a multimeter for custom troubleshooting if you’d like to test electrical continuity and actually confirm that the door interlock switch is running a current- but this isn’t at all necessary, since it’s extremely likely that replacing the door interlock switch will solve your problem.
Most microwaves actually include three switches behind the control board- a primary, secondary, and monitor switch. All of them along with the door latch assembly work together to prevent the microwave from running while the door is open.
You’ll need a Philips head screwdriver, needle nose pliers, and, of course, replacement switches, which you should be able to purchase from the appliance manufacturer at a minimal cost.
If you’d like to try to replace only one switch (it’s recommended you replace them all)- at step 3, you may use a multimeter to individually test each switching mechanism for a current. Any switch that doesn’t set off your multimeter is one that needs replacing.
Extreme caution should always be used if attempting home microwave repairs- microwaves will retain a dangerous charge even when unplugged for a period of time.
Why does my circuit breaker trip when I open my microwave door?
If opening your microwave door trips your circuit breaker, it’s probably an issue with the door interlock switch, or possibly a ceramic fuse. A malfunctioning or damaged interlock switch may be detected by the circuit as a fault and trip the breaker. Usually, replacing one or all off the interlock switches fixes this.
Is it dangerous to have a microwave running with the door open?
The answer in short is yes- if the microwave is actually running and it’s not just the lights and/or a fan spinning (as can be the case with some older models), it’s definitely not safe to be near, especially over prolonged periods- exposure to microwaves can cause severe eye problems at the very least. Unplug the microwave immediately if this is happening and troubleshoot or replace- safety first!
Can I do my own microwave repairs?
If the microwave is unplugged and it’s been left to discharge any remaining charge, it should be safe to attempt simple repairs like control board and door interlock switch replacement, however, caution should still be used as not to damage the microwave, and many manufacturers don’t recommend even common microwave home repairs for most people.
STAT: 90% of U.S. households own a microwave oven as of 2018 (source)
STAT: The heating capabilities of microwaves were discovered accidentally in 1945 (source)
STAT: Food and cookware taken out of a microwave is almost never hotter than 212 degrees (source)