Car door switches are one of the most basic, yet often overlooked items on any car alarm system. They detect if the door is open or shut so are the first layer of protection for any security system.
Even if you don’t have an alarm it's important that all of your door switches work, as without them you risk locking your keys inside your car!
Most vehicles have a timer that starts when you press the unlock button on your remote control. This timer is canceled if the car's body control module has detected a door being opened. If a door is not opened (or seen to be opened due to a faulty switch) the doors will re-lock. Typically after 30 seconds. Note; the timing can vary between manufacturers.
Most cars have a display in the instrument cluster indicating if a door is open, some will simply have one symbol for all doors, whereas others will show which individual door is ajar.
You may need to turn your ignition on for this display to work. Open each door one at a time (leaving the other doors closed) and see if the display shows that the door is open.
If your car does not have a display then turn the ignition on and see if the courtesy light turns on and off with when each door opens and closes (you may need to wait a couple of seconds for it to fade out on some vehicles). Of course, you’ll need a working courtesy lamp to do this test. If you don’t have a working one then check the fuses and the bulb as it's nice to have a working one when it gets dark!