Unplug your microwave from its power source.
Remove the top grill if you have a GE Spacemaker over-the-range model. Removing the grill requires you to remove a series of screws located either in front of the grill or just inside the grill opening. If you do not have an over-ther-ange model, remove the microwave trim. The trim is held in place by numerous screws located on either side of the microwave.
Remove the control panel. The control panel is typically held in place by one screw on top of the panel if you have an over-the-range model. For other models, the control panel is held in by one or more screws either on the top or top and bottom.
Make note of the control panel connections. If you need to, draw up a schematic or take a picture. Disconnect all wires from the control panel.
Look for the door switch on the left side. The switch looks similar to a dog tag and has two to three wires connecting into it, depending on your GE Spacemaker model. If you cannot locate the switch, your model may have a door that hides the switch. Open the door to reveal the switch. The door is usually plastic and opens with a gentle pull.
Disconnect all wires connected to the switch. Make note of how they were connected. Remove the switch. The switch is typically held in place by a clip. Insert the new switch in the same position as the old switch. Make sure that the clip is securely holding it in place. Plug in the wires.
Connect the wires back to the control panel and replace the control panel. Replace the grill or microwave trim.