How to Fix a Microwave Touchpad That’s Not Working
Membrane Switch
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:
Unplug your microwave before beginning this test.
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.
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.
If your test results indicate one or more keys are defective, you will need a replacement membrane switch.
Control Board
If you cannot key in numbers on your microwave touchpad but the display is still lighting up, it may be an issue with the control board. The control board supplies the touchpad with low voltage signals. When you press a button on your microwave touchpad, the control board sends a signal to the other microwave components to begin heating. If the membrane switch is functioning as usual, and the connection to the control board looks fine, then the control board likely needs to be replaced.
How to inspect a microwave control board:
Before beginning this or any other inspection, disconnect your appliance from the power source.
Locate your control board. You will need to remove all or part of the cabinet in order to access it.
Once you have found it, looking for any signs of damage or burning, visually inspect your control board.
If you find any issues while inspecting it, or if you have ruled out the other causes mentioned above, you will need a replacement control board.
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