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Will Anti Theft Light Drain Battery?

Ever wondered if your car’s anti-theft light could be slowly draining your battery? How about what it means when this light is continuously on or off? In this comprehensive guide, I debunk myths and lay out the truth about the impact of anti-theft lights on your car battery.

Key Takeaways: An anti-theft light doesn’t use enough power to drain your car batteries. It’s a low-powered device that only uses around 0.002 to 0.01 amps every time it flashes. Realistically, the chances of the anti-theft light draining your battery are close to zero.

Below ill go through the energy usage of these little red indicators, how they operate, the signs of a faulty anti-theft system, and what might be draining your battery if it isn’t the anti-theft light.

Effects of the Anti-Theft Light on Your Battery

The chances of the anti-theft light draining your battery are extremely low.

The anti-theft light uses up power every time it blinks. An anti-theft light uses around 2 to 10 milliamperes (mumps) to flash the light. It might seem like the anti-theft light uses a lot of power, especially if it’s blinking every few seconds, but it’s a low-power device.

A 2 to 10 mAmps anti-theft light uses 0.002 to 0.01 amp of power every time it blinks.

If we take the higher 0.01 amps as a constant draw, it will draw 0.01 amps continuously from the battery. In this case:

48 Ah ÷ 0.01 A = 4800 hours!

This means it would theoretically take around 4800 hours or about 200 days for the anti-theft light to completely drain a fully charged car battery if it constantly drew 0.01 amps!

Now Thats slow 🙂

A typical 12-volt car battery has around 48 ampere-hour (Ah) capacity. This means your car battery can supply 48 amps every hour. Even if you leave the anti-theft on, it will take an extremely long time for the anti-theft light to drain the battery completely.

If you’re still worried about the anti-theft light slowly draining your battery, remember that the alternator recharges your car’s batteries while the engine is running. The power usage of the anti-theft light is minimal if you’re using the car regularly.

What it Means When the Anti-Theft Light is On

The anti-theft light signals the owner that the car’s anti-theft system is turned on.

You might think doesn’t an anti-theft light defeat the purpose of an anti-theft system? Without the anti-theft light, you can’t determine if the anti-theft system is functional. Also, the light is an extra deterrent against thieves since it tells them that the car has an anti-theft system and stealing it would be difficult.

The anti-theft system and light will activate once the engine is turned off. It will only deactivate once the engine is reignited.

Signs of a Faulty Anti-Theft System

The anti-theft light indicates whether your anti-theft system is faulty or inactive. Some obvious signs of a faulty anti-theft system are:

  • The anti-theft light doesn’t activate when the engine is turned off.
  • The anti-theft light glows steadily instead of blinking while the engine is off.
  • The anti-theft light doesn’t turn off when you ignite the engine.
  • The anti-theft light still blinks when you use the correct car key to turn the car on.

If you notice any of these happening on your anti-theft light, consider having a mechanic or professional check out the car’s security system.

Possible Causes of Battery Drain

There are many reasons why your car battery is draining faster than expected. While the anti-theft light isn’t one of them, here are some of the likely culprits:

  • Defective Alternator
  • Old or Damaged Batteries
  • Parasitic Drain from Other Electrical Devices and Components (Headlamps, Hazard Lights, etc.)
  • Extreme Temperatures and Weather Conditions


International Research Journal of Engineering and Technology (IRJET). https://www.irjet.net/archives/V7/i6/IRJET-V7I6722.pdf

KIA. https://www.kia.com/ph/discover-kia/ask/what-causes-a-car-battery-to-drain.html

Video References


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About Alex Robertson

AvatarCertifications: B.M.E.
Education: University Of Denver - Mechanical Engineering
Lives In: Denver Colorado

Hi, I’m Alex! I’m a co-founder, content strategist, and writer and a close friend of our co-owner, Sam Orlovsky. I received my Bachelor of Mechanical Engineering (B.M.E.) degree from Denver, where we studied together. My passion for technical and creative writing has led me to help Sam with this project.

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