What Causes Both Battery and Brake Lights On?

If your car is showing both battery and brakes light on, it may be showing a serious underlying issue with your vehicle. In this post, we will try to diagnose and fix the cause which showed the error.

Car brake lights illuminate and appear on your dashboard for various reasons. Some of these causes are simple to repair without the need for a mechanic.

Others will necessitate the hiring of a car mechanic. It is to avoid complicating the problem further because they are challenging to resolve.

What Causes Both Battery and Brake Lights On?

car click when trying to start

When both the parking and brake lights illuminate, it indicates that your alternator is beginning to fail. While the battery may still be charged, it may not be charging at the required voltage of at least 13 volts.

Other possible causes include a faulty braking system that causes an increase in power consumption, a faulty connection, or a broken voltage regulator. Additionally, when both your battery and brake light on, it is sometimes the result of faulty electrical relays.

1. Reason Behind The Illumination

A car with parking and brake lights can turn on by itself for a variety of reasons. When a battery light illuminates the dashboard, it indicates a problem with the car battery charging, and when braking, it indicates braking errors.

2. Dead Alternator

car click when trying to start

If your alternator is undercharging, your battery will gradually lose power until your vehicle stalls. If the alternator overcharges – usually due to a faulty regulator – your battery cells will be damaged, and your battery fuse will most likely blow.

When the alternator fails, the battery will use whatever charge it has and the car will stall.

3. Worn-Out Brake Pads

mercedes c280 jerking on stop

Worn-out brake pads can cause car brake lights to illuminate. Because of the worn-out brake pads, the brake fluid level drops. The drop in brake fluid level causes caliper pistons to penetrate much deeper into the rotor.

When the sensor wire makes contact with the rotor, the car brake light can be forced to illuminate. It activates the brake pad warning light or the car brake light.

The solution to turning on the car brake light is to replace worn-out brake pads with new ones.

4. ABS

When there is a problem with the car’s antilock brake system, the brake lights may illuminate. Among the causes of this issue are an electrical malfunction and a dirty wheel speed sensor.

A mechanic should be consulted if your car brake light illuminates due to a faulty antilock brake system.

5. Wiring Damage

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A faulty wire or a loose connection will cause your ECU to report a possible fault with your brake and charging systems at the same time. Because wires deteriorate with age, it is worthwhile to inspect your wire harness from the battery. A faulty wire or a loose connection can cause short and damage to components of your vehicle.

It would also help if you cleaned the terminals of your battery and tightened the connectors.

6. Dead Battery

If your battery is failing or dead, your dashboard may show a battery light. It occurs when your battery’s electrodes begin to wear down, resulting in a voltage drop.

2. Fixing The Issue

A brake light indicator on your dashboard, next to the odometer, could be caused by a number of factors. Some of these issues can be handled on your own without the assistance of a professional. However, you will need a mechanic for specific issues to avoid making the situation worse.

1. Examine Your Car’s Battery

Examine the terminals of the battery for signs of damage or corrosion. Clean the corrosion and secure the clamps on the battery terminal correctly.

2. Examine the Alternator

Examine the alternator for any missing or loose components. Tighten any loose connections you discover. If you want to check the alternator at home without any specialized tools follow the steps

  1. Get yourself a voltmeter.
  2. Clean the battery terminals
  3. Connect the voltmeter to the battery terminals
  4. While the engine is turned off, you should get a reading of 12.5v – 12.8v.
  5. Now start the engine and look for higher readings, ideally over 13 – 13.5v.
  6. Turn on your radio, headlights, and other electrical devices.
  7. You should get roughly the same reading as before.
  8. A lower reading means your alternator is undercharging the battery.
  9. A higher reading means your alternator is overcharging the battery.


Q. Can You Drive While The Battery And Brake Light On?

A. Under no circumstances should you drive your car while these warning lights are illuminated on the dashboard. The car is informing you that there is an issue with the charging and braking systems. As a result, you should consult a specialist.

Q. What Causes Parking Brake Light On While Driving To Illuminate?

A. Various sensors evaluate and ensure that your vehicle’s systems function as intended. When there is a problem with your car’s braking system, your brake light will illuminate, while your battery light will shine to alert you that there is a problem with your battery charging system.


Many factors can cause the battery and brake light on. If any of these lights on your car dashboard illuminate, determine the source of the problem right away. If any of your warning lights illuminate, do not become alarmed. Find a safe place to stop and inspect your vehicle.

If everything appears to be in order after a visual inspection, restart the vehicle. It should have fix the cause of the issue!

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