Battery Light And Brake Light On? Everything You Need to Know

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battery and brake light on at the same time

Whenever your vehicle’s brake light and battery light activate simultaneously, there is often an underlying issue. Several sensors and sending units within your vehicle monitor all the processes and ensure that all systems function as expected. The brake light will illuminate anytime there is an issue with your braking system. In contrast, the battery light will illuminate once there is an issue with your battery charging system or the battery itself.

However, what might cause these warning lights to activate altogether, and what should be done if this occurs? In this article, we’ll cover all you need to know about your car’s brake lights and battery lights that illuminate at the same time and examine the reasons and possible remedies for this issue. Read on to learn more!

Brake And Battery Lights Activates Simultaneously: What Does it Mean?

Your vehicle’s brakes and battery are two entirely different systems within your car. However, when your battery and brake lights illuminate altogether, there’s a significant probability that your car’s alternator is failing. Although it can potentially charge your battery, it might never be doing so at the minimum voltage of 13 volts.

Other potential causes include a problem with your braking system that causes an upsurge in power usage, a faulty connection, or a broken voltage regulator. Also, when your brake and battery light is both on, it’s sometimes the result of faulty electrical relays or sensors that generates an error signal that activates these warning lights.

Probable Causes Why Your Battery and Brake Warning Light Is On

Why would the battery and parking brake lights simultaneously illuminate? Below, we’ll examine the critical causes of why your vehicle might throw these two different warning lights from two different systems simultaneously.

1. Faulty Alternator

In some circumstances, when car owners bring their vehicle to a shop vehicle with this kind of issue, a bad alternator often causes the problem. Even though you can check and diagnose the issue at home, experts always suggest taking your automobile to a specialist since they have the necessary equipment and experience to repair it.

Below is a brief instruction on testing your car’s alternator at home using a multimeter or voltmeter.

How to Examine Your Alternator

Suppose you lack sufficient expertise; checking your alternator could be a complex process, but it’s really relatively simple. It’s crucial to remember that the voltage of various alternators may range from 13 volts to 15.5 volts, based on the vehicle type. If you apply the instructions listed below, you’ll be able to determine if you have a failing alternator or not.

  • Take your voltmeter.
  • Make sure the terminals of your battery are dry and clean.
  • Attach your voltmeter to the terminals of your battery.
  • It would be best to notice between 12.5v and 12.8v while your engine is off.
  • Then start your engine and watch for higher voltage measurements, preferably between 13 volts and 14 volts.
  • Start engaging your vehicle’s headlights, air conditioner, stereo, and other electronic devices.
  • You must be generating roughly the same voltage measurement as before.
  • A lesser reading indicates that your alternator is undercharging your battery.
  • A more significant number indicates that your alternator is overcharging your battery.
  • It’s best to consult an auto repair for a complete diagnosis if the voltage readings are inaccurate.

How Much Is The Alternator Replacement?

The cost of an alternator replacement varies widely based on the year, model, and make of your vehicle. Therefore, you can expect to spend $250 on the component alone and around $200 on the service.

2. Malfunctioning Voltage Regulator

If you’re into cars, you’ve probably been exposed to a wide range of issues with vehicles. On particular cars, brake and battery lights flashed for brief intervals. It was discovered that a faulty voltage regulator caused the problem. In a nutshell, a voltage regulator maintains a constant maximum voltage across the circuit of your vehicle.

If you suffer a failing regulator, your car’s alternator could be overloaded or underloaded, leading to improper operation of your vehicle’s systems. For example, if your car’s brake system isn’t working correctly, you can notice that the battery light is on and the brake light is flashing.

3. Broken or Loose Wiring Connections

Your car’s Electronic Control Unit (ECU) will signal a potential problem with your braking and charge systems at the same time if the wiring or connection is weak, loose, or damaged. It’s a good idea to inspect your battery cables from time to time.

A short caused by a broken cable or a loose connection might harm your automobile’s electrical systems. Additionally, please make sure that your battery’s connections and terminals are free of corrosion, dry, clean, and securely fastened.

4. Failing Braking System

Your battery warning light could also come on if your car’s braking system suffers an electrical problem, which is uncommon but occurs unexpectedly! If all of the scenarios above fail, It’s best to inspect the wiring of your brake lines to make sure they aren’t corrupted or otherwise compromised.

What To Do When Your Brake and Battery Light Comes On

First, whenever your brake and battery warning lights come on while running your car, pull over to a safe place and check your vehicle. Switch off your engine and check beneath your hood for potential leaks or a burnt odor coming from the wiring. The stench of a burnt alternator is generally a sign of a problem.

If you see a brake light on your dashboard due to a low brake fluid level, you should investigate more. Ensure the battery terminals aren’t damaged and inspect for possible loose connections. After checking everything, you must drive your automobile home or into a shop before doing any repairs.

Why Does The Battery Light Come On?

A battery light can switch itself on for several reasons. Automobile battery charging issues are signaled by your dash battery light becoming illuminated. One or several of the reasons below is likely to trigger your vehicle’s battery indicator to flash.

Failing Or Dead Battery

To let you know if your battery is failing or dead, your vehicle’s dashboard might display a battery light. It happens when the electrodes of your battery begin to wear down, resulting in a voltage drop.

Faulty Alternator

Having a defective alternator means that your vehicle’s voltage is lower than it should be. Battery health will be compromised as a result. It’ll activate your automobile’s battery warning light.

Damaged Alternator Belt

A damaged alternator belt might also lead your battery light to come on. Cracks begin to form in your alternator belt throughout time due to the belt’s constant usage. Car batteries don’t get charged when this occurs. It triggers your dashboard to throw a low-battery warning light.

Corroded Battery Terminal

A deteriorated battery terminal might reduce the electrical conduction of your car battery since its terminals are the source of the battery’s power. It causes a battery charging issue that might activate a warning light to come on on your dashboard.

Broken Battery Cable

Whenever it disrupts the power flow, a defective battery cable might cause a vehicle battery light to illuminate. Your battery light might also be activated when the cable isn’t positioned correctly around your battery terminal.

Wiring Issues

Wires that carry electricity to your car’s charging system might break or get detached, causing a battery light to come on in some instances.  As a result, if there are problems with your charging system or electrical circuit, expect a battery light to come on.

Accessory Overload

Your battery won’t charge correctly if your alternator is overworked and too many electrical accessories are plugged in at once. Eventually, your battery indicator light will come on due to this problem.

Why Does the Brake Light Come On?

Various factors might cause a brake light indicator on your dashboard. It’s possible to address a few of these issues independently without needing to hire a professional. However, you’ll need a mechanic for specific issues to prevent making the situation even more difficult since they are challenging to solve. The following are some of the most prevalent reasons for an illuminated dash brake light that comes on by itself:

Parking Brake Not Fully Disengaged

The most common cause of a brake light coming on in a vehicle is when your parking brake is still engaged. When a driver misses or fails to release a vehicle’s parking brake fully, the brake light will come on. To resolve issues with a car’s brake lights, you must disengage your parking brake. Check your parking brakes or handle for damages once you’ve completed this and your brake light is still on. An experienced mechanic should only be called in if your automobile requires repair.

Leaking or Low Brake Fluid

Low brake fluid level is another factor that could cause your vehicle’s brake light to turn on and create other issues with your vehicle’s braking system. Brake fluid leaks can also be a significant factor in a low brake fluid level. When your vehicle’s brake light comes on, you’ll know right away what’s wrong with it.

If this is the situation, a brake fluid cleanout or repair might be necessary. As a result, you need to know how to monitor your brake fluid. It’ll keep your brakes from failing catastrophically. We advise you to switch off your vehicle and get it checked by a professional if you suspect a leak.

Worn Out Brake Pads

Worn brake pads might activate the brake lights on your vehicle. Brake fluid levels decline as a result of worn-out brake pads. The caliper pistons are forced to go deep into your rotor due to decreased brake fluid level. It’s possible to cause the vehicle’s brake lights to go on once the sensor line comes into contact with the rotor. It activates the brake warning light or your car’s brake pad light.

Malfunctioning Antilock Brake System (ABS)

The vehicle’s antilock braking system (ABS) might malfunction, causing the brake lights to illuminate. Electrical failure and a dirty wheel speed sensor are two possible reasons for this issue. A technician is an ideal person to call to fix a malfunctioning anti-lock braking system. For the best solution, we propose using the services of a skilled vehicle mechanic.

Burnt or Damaged Brake Light Bulb

A malfunctioning or burnt rear brake light bulb is another potential source of a flashing brake light on your dashboard. Once the bulb in your brake light burns out, the brake light on your dashboard may come on. The dimming of the rear brake lights is another possibility that might activate your dash brake light. This is a helpful thing for drivers who aren’t aware of the condition of the rear brake light. Drivers could prevent rear-end collisions when the car’s brake warning light comes on as you step on the brake pedal.


Don’t panic whenever you end up in a circumstance where your dashboard warning lights suddenly turn on simultaneously, don’t panic. Look for a safe place to pull over and check your automobile. After a visual inspection, if everything looks good, restart your automobile. Even if the warning lights go after restarting your car, it’s still advisable to have the situation evaluated by an auto repair. The essential thing to remember is that your dashboard warning lights came on for a purpose, and you must never disregard them.


Why does my brake and battery light come on at the same time?

Various sensors evaluate and ensure that your automobile’s systems operate as designed. Whenever there’s an issue with your car’s braking system, your brake light will automatically come on, while your battery light will come on to notify you that there’s an issue with your battery charging system.

Can a scanner clear my brake lights?

Yes, if your brake warning lights don’t go away after all the necessary fixing. A scanner can definitely clear any warning lights. In the case of brake lights, a decent scanner features a ‘cancel menu brake light’ option that can detect and fix any electrical issues associated with your brakes.

Can a bad alternator cause the brake light to come on?

Once your automobile’s alternator isn’t working correctly, the voltage it produces will be lower than it should be. It’ll have a negative impact on your battery’s performance and will activate your dashboard battery warning light.

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