How to Fix a Microwave
Repairing your microwave might seem like a difficult task, but more than 80% of our customers rate
these repairs as “easy” or “really easy.” On average these repairs should take less than 15 minutes to
complete. We break microwave repair down by common symptoms, like your touchpad is not
responding, your microwave is noisy, your tray will not turn, or your door is stuck. This step-by-step
guide teaches you how to troubleshoot. You will learn what parts are at fault, and how to test, fix, or
replace them.
How to Fix a Microwave Touchpad That's Not Working
If the buttons on your microwave touchpad do not work, it may be an issue with the membrane
switch. This part is made up of soft-touch electrical switches, which are two layers of Mylar plastic
with conductive coatings on the sides that face each other. When you press a key on your microwave
touchpad, the two surfaces come in contact and complete an electrical circuit which sends a signal to
the control board. The conductive coating on your membrane switch will wear out over time through
repeated use, and need to be replaced.
How to test a microwave membrane switch with a multimeter:
1. Unplug your microwave before beginning this test.
2. Locate the membrane switch in order to test it. You will need to remove the cabinet in order to
access the membrane switch, which is usually attached to the control board by a flat ribbon
connector.
3. After referring to the electrical schematic of your microwave to determine the matrix layout of the
membrane switch, test the touchpad with a multimeter. There should be a few ohms of resistance
when you test each key on the touchpad.
4. If your test results indicate one or more keys are defective, you will need a replacement membrane
switch.
How to Fix a Noisy Microwave
If an unusual noise is coming from your microwave turntable, the issue may be the drive motor. The
microwave uses a motor-driven coupler to turn the glass tray in your microwave. The motor should
be replaced if it is making a grinding noise.
How to test a microwave drive motor with a multimeter:
5. Unplug your microwave before beginning.
6. In order to access the drive motor, you will need to remove the appliance’s cabinet. The motor is
usually located in the bottom of the microwave and is held in place by a retaining screw and wires.
7. Remove the motor to test it for continuity. Set your multimeter to the highest setting and touch the
probes to the terminals. A properly functioning motor will produce a reading of zero.
8. If your microwave makes a grinding noise, or if the motor does not have continuity, then you may
need a replacement drive motor.
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:
9. Similar to other tests, begin by verifying that you have disconnected your appliance from the power
source.
10. 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.
11. 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.
12. If your test results differ from those above, you will need a replacement door interlock switch.
How to Fix a Microwave That Won't Heat
Your microwave may turn on but not heat up. This could be caused by a problem with the high
voltage diode, which helps to power the magnetron.
How to test a microwave high voltage diode with a multimeter.
13. Unplug your microwave before beginning this inspection.
14. Locate and remove your high voltage diode to test it for continuity. To access it, you will first need to
remove the cabinet and discharge the high voltage capacitor.
15. Set your multimeter to Rx1 and touch the probes to the terminals. Next, reverse the probes to check
for continuity in the other direction. You should receive a reading that shows continuity in one
direction, but not the other direction.
16. If your diode does not show continuity, or shows continuity in both directions, you will need a
replacement high voltage diode.