Most Kenmore microwave ovens have a door interlock switch that prevents the microwave from operating if the door is open. If either the switch or the door latch breaks, you won't be able to use your microwave until the faulty component is replaced. Before you install a new switch, ensure that it, and not the latch, is the component that's defective. Otherwise, you may end up replacing the wrong component and not repairing the microwave.
The interlocking door switch on a Kenmore microwave oven is a basic safety component that turns the microwave on and off, depending on the position of the door. The microwave can only work if the door is shut and the switch is latched. The switch is typically black and approximately an inch in length. It is usually attached to a bracket opposite the latch, which is located on the inside of the door. On the face of the switch are metal prongs or terminals that fit into entry ports on the latch when the door is closed. Certain Kenmore microwaves have as many as four door switches, and each one must be working properly for the microwave to operate when the door is shut.
Test the Switch
Test a door switch that you suspect is bad to confirm that it's broken prior to replacing it. Unplug your microwave. Remove the switch's harness or plastic case by depressing its locking tab lever on the side and lifting the harness away from the terminals. Set a multimeter to a resistance scale of Rx1. Attach one lead to each of the switch's two prongs so that one lead is connected to the common (COM) terminal and the other lead is attached to the normally open (NO) terminal. The multimeter should show a reading of infinity to indicate that the switch is open. Press the switch's actuator until you hear a click. Check the multimeter for a resistance reading of zero. If you don't hear a click or get a resistance reading other than zero, the switch has failed and must be replaced.
Replace the Switch
With your microwave still unplugged, discharge the high voltage capacitor to avoid electrical shock. Do this by taking a well-insulated screwdriver and touching it to each of the switch's terminals one at a time. Hold the screwdriver on the terminal for about five seconds. Don't be alarmed if you hear a loud pop; this is normal. Repeat the process until all of the switch's terminals have been discharged. Confirm that the new switch is the identical size and has the same terminal configuration and current rating as the old one. Loosen the screws of the existing switch, disconnect its wires and lift the switch off. Attach the wires to the new switch at the appropriate connections, line the switch up with the latch and tighten its screws until the switch is securely in place.
Any time you experience problems with a door switch, inspect its latch first. If the latch is loose or damaged, the switch won't be able to connect to it, and the microwave won't work. Reposition the latch by tightening its screws if it appears out of place or replace the latch if it's broken.