What it is: A small sensor or plunger switch usually built into the door frame or door latch.
• What it does: Detects when a door is open vs closed. When the door opens, the switch completes the circuit → tells the car to turn on dome lights, dashboard “door ajar” warning, and stop the power windows/locks from working on some cars.
• Where it’s found: On the door frame/jamb for older cars, or inside the door latch assembly for newer cars. Each door has its own.