Over the years, microwaves have become essential appliances in most people’s kitchens. So, what do you do when the microwave keypad stops working? Well, the good news is there is no need to throw out the microwave and buy a new one. By following this guide, you should be able to diagnose the issue and get the faulty part replaced. However, replacing parts in a microwave does require extreme caution to be exercised (see the safety warning).
Diagnose the Issue
A defective microwave keypad is usually the result of wear and tear over time causing the microwave’s controls to lose their sensitivity, which can be remedied by replacing the keypad. Alternatively, the keypad may not be working because of a fault with the microwave’s main control board.
Try pressing each of the buttons on the keypad. If some of the buttons respond correctly, while others do not, the keypad should be replaced. However, if none of the keypad buttons respond correctly, it is likely that the main control board is defective and that it will need to be replaced.
Faulty Keypad / Membrane Switch
The microwave’s keypad, sometimes called the touchpad, is a membrane switch. A membrane switch consists of two flexible layers of Mylar plastic with conductive coating on the sides that face each other. Pressing a key on your microwave keypad brings the two surfaces together, which closes the circuit and sends a signal to the control board. Over time, the conductive coating on the membrane switch will wear out, particularly for keys that are frequently used. The easiest way to fix the issue is to install a new keypad.
The control panel and keypad can be tested with a multimeter. However, you will require the wiring diagram and the ability to interpret the multimeter readings.
Defective Control Board
Following the input signals that the microwave’s control board receives from the keypad, the control board then sends signals to the other components of the microwave. When the control board fails to act on the commands from the keypad, it suggests that the control board is defective. If you remove the control board from the microwave, it can also be visually inspected for damage. You should look for signs of burning or disconnected wires. If the control board is defective, you will need to replace it.
The control board can also be tested with a multimeter. To test it with a multimeter, like the control panel, you will need the wiring diagram and the ability to interpret the multimeter readings.
Follow these instructions to remove and replace the control panel/keypad and/or microwave control board.
The high-voltage capacitor inside the microwave can store a lethal amount of electricity, even after the microwave has been disconnected from the power for several months. To safely access internal electrical components, the capacitor must be discharged.
Depending on the type of microwave and your level of microwave repair knowledge, it may be possible to repair the control panel or control board without touching components associated with the high-voltage capacitor; however, you would be risking fatal electrocution.
To Discharge the High-Voltage Capacitor
The capacitor can be discharged by touching both the positive and negative terminals of the capacitor with a metal screwdriver blade. You must insulate yourself against electrocution, and the terminals must be touched by the metal blade at the same time. You could use either a flat-edge screwdriver with a rubber handle or needle-nose pliers with rubber handles.
Remove the Control Panel and Keypad
On most microwaves, the keypad is part of the front control panel, and therefore the entire panel will need to be removed and replaced if the keypad is defective.
- Disconnect the power to the microwave.
- Access the control panel mounting screw. Accessing the mounting screw will depend upon the type of microwave you have. You may need to remove the grille first or remove the microwave casing that goes over the microwave.
- Unscrew the control panel mounting screw.
- Make sure to take a photo and to take note of how the control board connects to the main control board before disconnecting any wires.
- Before you can detach the control panel, you will need to unscrew the grounding wire and disconnect the wires to the control board.
- Detaching the control panel will depend on the type of microwave. You may need to lift the control panel and free it from the hinge tab or unscrew more mounting screws.
Detach the Control Board from the Control Panel
- Release the ribbon connector.
- Remove the screws that secure the control board to the control panel.
- Depending on the microwave, you may need to depress the retaining tabs and lift the housing out, or just lift the control board out.
Install the New Control Panel or Control Board
- Make sure to remove all the packaging and plastic.
- Place the control board inside the control panel.
- Secure the screws that mount the control board to the control panel.
- Connect the ribbon connector.
- Reattach the grounding wire to the control panel with its screw and washer.
- If applicable, insert the hinge tab into the front panel of the microwave.
- Reattach the wires to the appropriate terminals on the control board.
- Insert the control panel tabs into the front panel slots, and push the control panel down to secure it to the microwave.
- Secure the control panel with the mounting screw.
- Secure the screws to reattach the grille or microwave casing.
- Reconnect the power to the microwave, and run a test to ensure the issue is fixed.