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What to Do if the Door Ajar Warning Light Stays On

Stephen Fogel
February 11, 2019

Most cars today have a “door ajar” warning light on their dashboards. When the system is working properly, the light lets you know that one or more of your doors is either open or not closed securely. On some vehicles, the trunk lid, rear hatch and even the hood can be part of the system.

door ajar light

 

But the warning light system can sometimes malfunction. If this happens to you, it’ll be annoying — and if left unchecked, it could potentially drain your battery.   

How does the door ajar light work?

Each door in your car is equipped with a sensor that can tell whether that door is open or securely closed. The sensor typically uses a switch with a spring-loaded plunger that is compressed when the door is closed, and is released when the door is open.

This action opens and closes an electrical circuit, sending a signal to your vehicle’s computer, activating the door ajar warning light when the door is open. This sensor is often also connected to the interior lights that go on and off when a door opens and closes. 

If you notice the door ajar warning light while driving, you should pull off the road as soon as it is safe to do so and try closing all your doors again. That should fix the problem.

However, a fault in either the electrical or mechanical components can cause the door ajar warning light to remain on when the doors are closed, and possibly cause the interior lights to remain on. 

 

Can I drive with the door ajar warning light on?

In most cases, it’s safe to drive your vehicle with the door ajar warning light illuminated, as long as you have checked that all of the doors and the trunk are securely closed. But if your interior lights remain on, that’s a different story.

Driving with the interior lights on can make it harder to see outside, can be distracting to other drivers, and is illegal in some places, Plus, if the interior lights are on constantly, including when the car is off, they can also drain your battery.

Additionally, the car’s computer might not let you lock the doors. This can be a safety issue when you are in motion, and a security issue when you park your car.

How can I fix my door ajar warning light?

Once you’ve determined none of the doors or latches are open, there is one easy thing you can try to fix your problem: Spray WD-40 into the door latches. 

This can resolve mechanical issues, such as sticky latches and gummed-up switches. Spray the WD-40 liberally, and open and close each door firmly a dozen times, to work the lubricant into the mechanisms. Apply more WD-40 and repeat.

If the WD-40 fix does not turn off the light, we recommend having a mechanic take a look. A repair shop might do one of the following to fix it: 

  • Replace defective door switches or electrical components: One or more of your door ajar warning light switches may be broken or worn out, or could be causing a short in the system. There might also be a fault in your car’s computer. Your mechanic can troubleshoot the door ajar warning light, identify the problem and repair it.
  • Repair any structural causes: Vehicles that have had crash damage to their doors may have switches that don’t shut off properly when the doors are closed. This can also happen to older vehicles, whose doors may have sagged and are out of alignment. A mechanic or a body shop can repair the doors.
Stephen Fogel

About the Author

Stephen has been an automotive enthusiast since childhood, owning some of his vehicles for as long as 40 years, and has raced open-wheel formula cars. He follows and writes about the global automotive industry, with an eye on the latest vehicle technologies.

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