Model # GERA205PWH4
, all the functions on this range would operate properly, but when the customer was finished cooking, pressing the 'OFF' button would not respond to touch. The only way the customer was able to turn off any of the oven functions was to cycle the power at the circuit breaker. Not the safest situation to have in your house, so this one needed to get fixed right away.
Many appliances will utilize a touch pad membrane switch to accept user inputs to the electronic control boards. These switch arrays consist of buttons that look like bubbles in the membrane material. Each switch will have electrical contacts mounted to the top and bottom of each button that are separated by the raised bubble of the switch. When the button is pressed, the two contacts will touch and close an electrical circuit to the control board which responds based on the keypad pressed.
Because touch panels can have many buttons mounted within the membrane, a keypad matrix will be used to reduce the total number of wires required by the control board to monitor each button. In the example above, we would need 18 wires to complete the circuits of these 9 switches, or if a common neutral was used, 10 wires. But when a switch matrix is used, 6 wires will accomplish the same task. A very effective method but it does come with one significant fault, which we can use to our trouble shooting advantage. If any one wire in the matrix were to become damaged or no longer make an electrical connection, all switch contacts connected to that wire would no longer function.
Back to the range I was working on, all the buttons were functioning properly with the exception of the 'off' key. Because I didn't know the pattern for the matrix (sometimes it's printed in the tech sheet) I had to use my meter to take some readings in order to located the pattern myself. What I found on this key pad was the off button is not a part of the matrix like the rest of the buttons, but rather has two dedicated wires running to it. And when I did a resistance check between the two 'off' button contacts, I had an infinite resistance reading whether it was pressed or not. So this key was definitely bad requiring the entire membrane to be replaced.
With a new switch membrane installed in this unit, all the buttons works as expected, and the customer no longer needed to run to the garage to shut off the breaker.
Membrane Switch Part # 9762104