Battery and Brake Light on (Causes)

Brake and Battery Light on (Causes)

Battery and Brake warning lights

Regarding dashboard warning lights, brake, and battery lights are the two most frequently illuminated. 

Battery and Brake Light on

Seeing them light up simultaneously can be perplexing, leaving drivers unsure of the underlying problem. That’s why at Automotivedroid, our team of experts is committed to providing readers with the most comprehensive and accurate information available, so you can be confident in diagnosing and fixing any issues with your vehicle. 

The most common causes of a brake and battery light on and off simultaneously are a faulty alternator, poor connections between the battery, and a dead battery.

In this post, we’ll delve into the common reasons for brake and battery light activation and offer advice on addressing them. So, let’s get started!

Reasons why your Brake light and Battery light on at the same time:

The main reason behind the brake and battery light simultaneously can be a bad alternator. This is the most common cause. Also, lousy battery connections can cause both the brake and battery light to come on. 

This is because the alternator is not getting enough power from the battery to charge it. The solution is to clean the battery terminals and ensure they are tight.

Battery and brake light on could indicate multiple electrical system issues with your vehicle. The most likely causes are:

  • A faulty alternator (the device that charges your battery)
  • Poor connections between the battery and other components in the system
  • A dead battery

Testing The Alternator:

You will need a voltmeter to test your car’s battery connections if you ever see the sign of battery and brake light on at the same time. The process is simple: connect the positive lead of the voltmeter to the battery’s positive terminal and the negative lead of the voltmeter to the negative terminal. 

If the voltmeter reading is 12 volts or higher, your battery functions appropriately. If it reads less than 12 volts, this could indicate bad battery connections.

Battery and Brake Light on (Causes)

Several symptoms can signal bad battery connections. If you’re having trouble starting your car, weak battery connections could be the culprit. Dim headlights or electrical issues can also be signs of lousy battery connections.

If you suspect that you have bad battery connections, the first step is to clean the terminals. You can do this by using a wire brush or sandpaper to remove any corrosion that has built up on the terminals. 

Once clean, tighten the terminal clamps to be snug against the battery posts. You can apply a terminal protector such as Vaseline or dielectric grease to protect the terminals from future corrosion.

Maintaining good battery connections is crucial for your vehicle’s overall performance. Regularly checking and cleaning your battery terminals can help prevent future issues and ensure your car starts smoothly.

Bad Alternator Symptoms:

If you’re experiencing the warning sign of brake and battery light on at the same time, you must schedule an appointment with a professional mechanic to have your alternator replaced as soon as possible.

Here are all the signs of a faulty alternator:

  • A faulty alternator might cause your car to stall regularly or have trouble starting.
  • Another warning sign of a damaged alternator is a whining or screaming sound that occurs after the car starts.
  • Dim or very bright lights could also indicate a bad alternator.
  • If you smell burnt tires or electrical wires, your alternator may be faulty.
  • A lousy alternator may also be indicated by a dead battery, an illuminated battery, or a brake light turning on.

If you notice any of these signs, you must schedule an appointment with a professional mechanic to replace your alternator immediately. 

Preventing Alternator Problems:

  • Maintaining your car batteries properly might also prevent issues with the alternator. Avoid stopping the automobile for extended periods, and don’t use electronics when the engine is off. 

These actions may deplete the battery and trigger an excessive alternator overcompensation that harms the voltage regulator.

  • Inspecting your alternator and battery capacity is crucial if you wish to equip your automobile with high-powered electrical accessories. 
  • It may be necessary to change these components to ones with greater amperages since these attachments require more power than the original alternator can provide.

By following these tips, you can increase the durability of your alternator and prevent problems from arising.

Testing and Fixing Battery Connections issues:

Testing battery connections:

You’ll need a voltmeter to test the battery connections in your car in case of battery and brake light on at the same time. The steps are straightforward: attach the voltmeter’s positive wire to the battery’s positive terminal and its negative wire to the battery’s negative terminal.

Your battery is in good condition if it displays 12v or more when tested with a voltmeter. A low voltage reading could indicate poor connections if it’s less than 12v; however, other issues that prevent full power from reaching your starter relay unit (the part that turns on your lights) may exist.

Signs of loose battery connections:

When it comes to a vehicle’s performance, the battery connection plays a significant role. In case of lousy battery connections, several symptoms can manifest and on of the is the brake and battery light on at same time. The only sign is difficulty starting the car, which can be attributed to poor battery connections leading to a weak power supply.

Another significant symptom to look out for is dimming headlights, which can indicate a low power supply reaching the headlights. Furthermore, if your car is experiencing electrical issues like flickering dashboard lights or broken power windows, it could also be a sign of lousy battery connections.

It is essential to regularly inspect and maintain the battery connections to avoid any inconvenience on the road. Any signs of poor battery connections should be addressed immediately to prevent further damage to the vehicle.

Fixing Bad Battery connection Issues:

In case of suspicion of lousy battery connections for dashboard showing battery and brake light on at the same time, it is recommended to initiate prompt remediation steps to avoid any further damage to the vehicle. The first step is to clean the battery terminals thoroughly to remove any buildup of corrosion. This can be achieved using a wire brush or sandpaper to scrape off the corroded material.

Once the terminals are clean, it is essential to check the tightness of the terminal clamps and ensure they are firmly secured against the battery posts. This will help provide a stable and consistent power supply to the vehicle’s electrical components.

A terminal protector should be applied to the terminals to prevent future corrosion. This can be Vaseline or dielectric grease, which can be carefully applied to the terminals. This will protect the terminals from further corrosion and ensure optimal performance of the battery connections.

It is important to note that any indication of lousy battery connections should be taken seriously and addressed promptly to avoid any inconvenience on the road.

Proper maintenance and care of the battery connections can ensure a smooth and uninterrupted driving experience.

Testing A Bad battery:

If your car’s dashboard shows the brake and battery light on at the time you need to test your battery for safety:

  • Drop test: A simple way to test a car battery is the drop method. Hold it about 2-3 inches above a hard, flat surface and let go. If the battery bounces when dropped, its charge has probably run low; fresh batteries will plop down without bouncing.
  • Voltmeter test: For more accurate results, test your car battery using a voltmeter. The positive and negative terminals of the battery are located near its base—they should be marked with “+” or “-” signs.

Touching the positive and negative leads to corresponding battery terminals, and your multimeter will produce a reading within just a few seconds. If fully charged car batteries have 12.6 volts of charge or more, it’s time for another round of road-tripping adventures!

  • Load test: To get the most accurate results, perform a load test with alkaline batteries. A load test gauges how well the battery functions while it’s in use.

For a car battery, set the multimeter’s voltage dial to 12V and hold one probe on each end of the battery. The meter should register from 10 to 15 milliamps (mA).

If your car’s battery shows readings of less than 400 or 500 milliamps, it is time to consider replacing it.

  • Professional test: If you have doubts about how to test a car battery or if it’s been acting up, take it to a mechanic.

They have the expertise and equipment to accurately diagnose and test car batteries. They can help determine if a battery is wrong or if there’s another problem with your electrical system.

Faulty Car Battery signs:

A damaged car battery can cause several typical symptoms, such as a slow or nonexistent engine crank when you turn the key, weak or flickering headlights, trouble starting the car, frequent stalling, or a loss of power when climbing hills.

If you’re experiencing any of these issues with your vehicle—even if they appear minor—it’s imperative that you have them checked by an auto mechanic immediately. 

While many factors could be causing these symptoms (and therefore preventions), one thing is sure: ignoring them could result in significant safety risks if something goes wrong while driving under low electrical voltage conditions (like having no power).

How to change a car Battery?

If your car ever shows a warning sign on your dashboard of brake and battery light on simultaneously, you might see many different issues. One of them can be a bad battery; in that case, you need to change the battery completely. For that, we are here with all the steps on how to change your car battery:

  • 1. Turn off the engine and remove the keys from the ignition. Make sure the car is in the park and the parking brake is engaged.
  • 2. Locate the battery under the hood of the car. The battery may be covered by a plastic cover or held in place by a bracket.
  • 3. Locate the negative (-) and positive (+) terminals on the battery. It’s important to disconnect the negative terminal first to prevent any electrical shorts.
  • 4. Use a wrench or pliers to loosen the nut on the negative terminal and remove the cable from the battery. Repeat the process for the positive terminal.
  • 5. Remove any brackets or covers holding the battery in place. Lift the battery out of the car and place it on a flat surface.
  • 6. Clean the battery terminals and cable connectors with a wire brush or battery cleaner.
  • 7. Place the new battery in the same position as the old battery. Make sure the positive and negative terminals are in the correct positions.
  • 8. Reconnect the positive (+) cable to the positive terminal and tighten the nut with a wrench or pliers.
  • 9. Repeat the process for the negative (-) cable.
  • 10. Secure the battery in place with any brackets or covers that were removed earlier.
  • 11. Start the engine to make sure the new battery is working properly.
  • 12. Dispose of the old battery properly at a recycling center or auto parts store.
Final Thoughts

Your alternator may fail if you notice that your car shows warning sign of brake and battery lights on.

It is critical to solving the problem as soon as possible because a broken alternator can result in a dead battery.

It is advisable to have your alternator regularly checked and keep the battery in good condition to avoid future problems. Awareness of warning symptoms might also help prevent more serious issues from arising.

If the battery terminals are dirty or corroded, cleaning them, and tightening the clamps can fix faulty connections. Terminal guards can be used to prevent corrosion from forming in the future.

The best action is to replace a battery that cannot be repaired. In addition, it is essential to perform routine maintenance on your vehicle and pay attention to warning flags as soon as you see them for the engine in your car or truck to run with peak efficiency.


A: No, it is not safe to keep the battery and brake lights on while driving. These warning lights point to a braking system or charging system issue, which may result in brake failure or a dead battery.

A: Indeed, a malfunctioning alternator can make both the brake and battery lights come on simultaneously. This is so that the alternator, which powers the car’s electrical system and charges the battery, can do its job.

It can cause the battery to discharge and the brake system to break down, which will turn on both warning lights if it is not working properly.

To prevent any potential safety concerns, it’s crucial to have your car checked by a qualified mechanic as soon as you detect both lights go on at the same time.

A: The cost to fix a bad alternator can vary depending on the make and model of the car, as well as the location and labor costs. On average, the cost can range from $300 to $700.

A: If the alternator or battery connections have been repaired but the brake and battery lights still come on, there may be another issue with the vehicle’s electrical system. To identify the problem, it is advised to have the car inspected by a qualified mechanic.

A: The brake and battery lights can indeed turn on due to a faulty battery. The brake system may malfunction and set off the warning lights if the battery is not keeping a charge or is not providing enough power to the electrical system.

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