How to Fix a Microwave That Won’t Stop Running

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A microwave has become a crucial appliance to have in the kitchen, so much so that you may worry about the day when it stops running. However, what most homeowners don’t expect is for their microwave to have the exact opposite problem. If your microwave is working too well and won’t stop running, it is just as jarring a problem as a microwave that won’t work at all.

The good news is that if your microwave keeps running even if the door is open, you’re not going to receive the mythical dose of radiation that the old wive’s tales may say you will. However, it is not something that you should just let happen. When a microwave won’t stop running, you need to unplug it so that you can diagnose the problem.

When a microwave won’t stop, there are two situations that can help you accurately diagnose the problem.

  • The microwave runs with the door closed. If the microwave only continues to run with the door closed and won’t stop no matter how much you slam the “Stop” button, then it is most likely a control board issue. If it stops when the door is opened, it means the switch is shutting off the power as it should be, but the control board is not sending the correct shut-off signals when it does have power or one of the door switches has failed.
  • The microwave runs with the door open. If the door continues to run even when you open the door, then it is likely a door interlock switch fault. When your microwave door latches, the latch connects to a switch, which when it activates, allows the microwave to receive power. If this switch has gone faulty, it can cause the microwave not to run at all or it can cause it to stay active even when the door is open.

Replacing the Correct Parts

Depending on the symptoms, you have narrowed the problem down to either the control board or the door interlock switch in your microwave. Both can be tested for continuity with a multimeter, but because the symptoms are so specific to the problems, you may not need to test it, just replace it.

Unfortunately, the real issue with microwaves is that they can hold a lethal electrical charge even when unplugged. You may need to discharge the capacitor for your own safety. Do not attempt this if you have not had the proper training.

To replace the control board, you need to remove the outer cabinet and will find it located behind the touchpad. If you do end up testing the control panel and find it is still working, then you may actually have a problem in which the control panel relays have gone bad. If that is the case, then only the relays will need to be replaced.

Replacing the door interlock switch is actually in the same general area as the control board. The switch will be mounted near the touchpad to the area where the door meets the cabinets since it requires the door latch to touch it in order to activate. While the switch is a little more difficult to recognize, it is easier to remove and replace than a control board. The most difficult part is reaching it and finding the screws that need to be removed in order to unmount it. Unlike the control board, if the microwave is running with the door open, it can only really mean a faulty switch so there isn’t really much need to test it. However, you can if you want to.

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