Faulty Car Door Switches: Testing, Repairs & Replacements

Car door switches: How to test, repair, and replace.

Car door switches are one of the most basic, yet most overlooked, parts of a car alarm system. Their job is simple: to detect whether a door is open or closed. This makes them the first line of defence for any security setup.

Faulty car door switches can cause issues

Even if you don’t have an alarm fitted, it’s important that all your door switches are working properly. If they fail, you could accidentally lock your keys inside the car.

Most vehicles with keyless entry systems run on a timer once you press the unlock button on the remote. That timer is cancelled as soon as a door is opened. If a faulty switch prevents the system from recognising the door opening, the timer will keep running, and the vehicle will automatically re-lock. This usually happens after about 30 seconds (timing varies between manufacturers).

Faults caused by dabbling!

Sometimes switches simply fail with age and need replacing. Other times the switch has been tampered with by someone who has not considered the consequences before doing so.

The dumb tradie!

Some people like to sit in their van for smoko and listen to the radio with the door open, but this causes the door open warning chime to sound which annoys them.

One daft solution is to use some tape to hold the switch in the closed position. This is easy to spot as shown in the photo.

The more sophisticated idiot will unplug the switch or cut the wire to the switch.

I then have to do some detective work to find out why the van locks itself randomly. I like to call these issues a user interface error.

Testing your car door switches

Most cars have a display in the instrument cluster that indicates if a door is open. Some vehicles use a single warning symbol for all doors, while others will show exactly which door is ajar.

To test:

Turn the ignition on (if required for your car’s display).
Open each door one at a time while keeping the others closed.
Check whether the display shows the correct door as open.

If your car doesn’t have a display, you can use the courtesy light instead:

With the ignition on, open and close each door one at a time.
The courtesy light should turn on when a door is opened and turn off when it’s closed. (Some vehicles may have a slight delay or fade-out effect.)

Note: A working courtesy lamp is needed for this test. If yours isn’t working, check the bulb and fuses. It’s good to have working lights when it gets dark!

Repairing your car door switches

Inspecting the switch

If, after testing your car’s door switches, you find that one isn’t working, it will usually need to be repaired or replaced.

For simple push-in switches (like the one shown in the photo), you can use a screwdriver to remove the switch and inspect it. Look for corrosion or dirt on the contacts, and clean them if necessary.

Some door switches, however, are fully sealed and can’t be serviced. In that case, the best solution is to replace the faulty switch. You can typically order a new one from your local dealership or an auto parts supplier.

Can’t find the door switch?

If you don’t see a visible switch below the door latch or hinge, your vehicle may have the switch built into the door latch itself. This design is common in boot switches and on some late-model vehicles. These switches can also fail, but replacement isn’t always a simple job.

I always test the door switches when carrying out a car alarm installation, so will let you know if a replacement is needed.

If you already know your switch is faulty, please let me know before I start work. I’m usually happy to fit a new one for you if you bring the replacement part along. I’m also happy to work with you to get the replacement switch.

Best place to purchase a replacement car door switch?

If you are in a rush, then I’d suggest the local car dealership, but they can often be overpriced. If your car comes from Japan or Europe then I recommend checking out amayama.com, especially if you require more than just a single part.