Will Door Ajar Light Drain Battery?

Often car owners commonly encounter situations where the door ajar light of their car suddenly comes on.

But will the door ajar light drain the battery, and what causes the light to turn on like that?

The door ajar light can come on due to several reasons depending on the vehicle’s model, and when this malfunctions, it can potentially drain your car battery.

In this article, let’s find out the potential reasons causing the door ajar light to stay on and learn more briefly about other common reasons which can potentially drain a vehicle’s battery.

What Is the Purpose of a Car’s Door Ajar Light?

Typically, the door ajar is a Warning Light sensor located on the instrument panel of any vehicle.

This light will illuminate whenever one of your vehicle doors is not closed properly, and as soon you securely close all the doors, this warning light will automatically turn off.

Remember, your vehicle’s electrical system is the main driving force behind your car door sensors. Every existing internal car sensor features a specially designed signal delivering function, which sends the signal that indicates whether the electrical circuit is currently open or close. 

Therefore, the main purpose of a door ajar sensor is to recognize whenever you left any door slightly open or entirely open on your vehicle and alert your vehicle’s Electronic Control Unit or ECU about this action.

Then, you will see an icon light up on your vehicle’s dash to let you know that a door is still not closed securely, and eventually, the icon will turn off as soon you close the door properly.

Will Door Ajar Light Drain Battery?

Yes, it can. If you leave your car door open for a longer period or if the warning light sensor malfunctions, it can potentially cause the battery to drain.

If you fail to close the doors or trunk of your car fully, your car’s interior lights will continue burning the energy and as a result, the battery will be draining until you notice it and take proper action.

Even for some vehicle models, leaving the door slightly ajar can also cause the internal or door lights to illuminate, and if the lights stay on like that for long enough, your vehicle’s battery will drain.

Why Does the Door Ajar Light Come On?

As I have already mentioned earlier, there can be several reasons behind your door ajar warning light sensor keeps coming on depending on your vehicle model and type.

Therefore, let’s have a look at other potential reasons-

  • It can occur due to an electrical short in the dome light.
  • The warning light sensor can turn on when an electrical short occurs in the anti-theft system
  • If your car door switch gets stuck in the “Open/On” position, the door ajar light will stay on until you fix it.
  • Even due to exposed wires, this light might stay on.
  • An electrical short in any of the door switches.

Note: The occurrence can also arise due to mechanical error or malfunctioning. So, make sure to bring your vehicle to the nearest car repairing shop for getting a proper diagnosis by professional experts.

Have a look at this How to Fix a Door Ajar Light on Any Car video to learn an easy fixing method.

What Causes the Vehicle Battery to Drain?

Besides the door ajar warning light malfunctioning, your vehicle’s battery can also drain quicker than it is supposed to due to some other possible reasons.

So, let’s have a brief idea about all those potential reasons from here-

Leaving Vehicle’s Headlights On:

It is the most common reason for vehicle battery-draining since many people often forget to turn off the headlights after parking the vehicle safely.

Even in some modern vehicle models, the headlights are designed in a way, you need to turn off the headlights after a certain time.

So, make sure you are well aware of your car’s type and how to control all the electrical components correctly.

Due To Parasitic Drain or Draw:

While you are driving or your vehicle’s engine is on, the alternator will recharge the battery, so even if you are using multiple electrical devices at a time, the battery will not die or drain that much.

But when your vehicle’s engine is not running or shut off, the alternator cannot recharge the battery like before, which will cause a little electrical mishap and will drain your vehicle battery entirely. This type of battery strain is known as a parasitic drain or draw issue.

Prevent it by ensuring that all lights are off as well as all doors including- the trunk and glove box are fully closed.

Old Worn-Out Battery or Loose Connections of Battery Terminals:

Another common reason behind vehicle battery draining is when your battery eventually turns old and wears out severely.

In case of broken or severely damaged battery condition, there is no other way than to replace it.

But if you notice a loose wire or terminals connection or the battery connecting wires get heavily corroded with an excess amount of debris, you can fix them by cleaning and tightening. In both cases, you should diagnose first to confirm which one is the case.

Also, you can prevent corrosion problems in advance by cleaning your vehicle’s battery terminals regularly, and this HOW TO CLEAN BATTERY TERMINALS will guide you on that task.

Due To Extreme Weather Conditions:

Indeed, any harsh weather condition will directly affect your car battery, whether it’s a freezing winter or boiling summer season.

Although most new vehicle batteries have better resistance to cope with extreme seasonal temperatures, used or older batteries will not survive in intense cold or heat conditions.

 Harsh conditions will dilute used or an older battery’s performance level and even can force it to die completely.

Due To Alternator Failure:

Since your car battery relies on the alternator during the drive so, if the alternator malfunctions and does not work correctly, the battery will not get enough charge. Due to an insufficient charging facility, the battery will eventually drain completely.

Because Of Too Many Short Drives:

Cranking the engine takes a tremendous amount of power from your battery, but as mentioned previously, the alternator recharges your battery while the engine runs.

Generally, when you take too many short drives so quickly, the alternator can potentially fail to recharge the battery properly.

When your battery is getting older, it will drain quickly during frequent short drives.

How Long Does the Door Ajar light Will Take Emptying Your Car Battery?

Generally, the car battery will eventually drain with time and depending on the level of use. It will be pretty difficult to answer the exact duration of any used battery to entirely drained due to the lights keeping on.

But if your car battery is relatively new and you have fully charged it, the following estimation might give you an idea of the proximity.

On average, vehicle batteries have around 45 Ah capacity as well as 12 electrical system voltages, and the small warning lights are 10 watts per piece.

Therefore, if you have accidentally left a door open or the interior lights on for the whole night, your car battery might become empty after twenty-seven hours.


Whenever vehicle owners notice that their door ajar lights come on or stay on, the first concern that pops into their heads is whether this condition will drain the vehicle battery or not. That’s why I tried to explain the answer simply in today’s article.

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