How to Fix a Microwave That Will Not Shut Off

If your microwave continues running when you open the door, it may be a problem with the door interlock switch. A functioning door switch provides power to other components of the microwave and should interrupt power when the door is open. The components that could stay on when the door is open, but the door switch isn’t working are the fan motor, stirrer motor, and interior light. There is a hook or latch on the microwave door which activates the door switch, located inside the cabinet.

How to test a microwave door interlock switch with a multimeter:

1. Similar to other tests, begin by verifying that you have disconnected your appliance from the power source.
2. Locate and remove the door interlock switch to test it for continuity. You will need to remove the microwave’s cabinet in order to access it.
3. Using a multimeter set to Rx1, ensure the button is depressed and touch the terminals with the meter’s probes, you should receive a reading of zero or nearly zero, indicating that there is continuity. Next, with the probes still touching the terminals, ensure the button is not pushed in, this test should indicate that there isn’t continuity.
4. If your test results differ from those above, you will need a replacement door interlock switch.

If your microwave doesn’t shut off when you press the stop or pause button, but does stop when you open the door, there may be a problem with the smart board. The smart board, sometimes called the control board, controls the microwave by powering the relays. A sign of a broken smart board is not shutting off the relay when a function is complete, which is signaled by the time you put in on the touchpad being up. To find out if the smart board is the problem, you can test the relays for continuity.

How to test a microwave smart board with a multimeter:

1. Unplug your microwave before beginning; you will be handling electrical components.
2. Remove the cabinet of your microwave and locate the smart board, it will most likely be found behind the keypad.
3. With your multimeter set to Rx1, touch the probes to the output terminals of the relay to check for continuity. You should receive a reading of 0 when the relay is not powered. You should also inspect your smart board for any signs of burning or damage.
4. If your test results show that there is continuity when the relay is not powered, you will need a replacement smart board.