Third Brake Light Not Working: Quick Fixes and Troubleshooting Tips

The third brake light, also known as the center high mount stop lamp, is an essential safety feature in modern vehicles.

Its purpose is to alert drivers behind you that you are applying your brakes, reducing the likelihood of rear-end collisions.

However, like any other car component, the third brake light can malfunction, leaving you wondering what went wrong and how to fix it.

Third Brake Light Not Working

Understanding the common causes of third brake light failure and taking proper troubleshooting steps is crucial to ensure the safe operation of your vehicle.

This article will delve into the possible reasons for this issue and guide you through the process of diagnosing and resolving the problem when your third brake light stops working.

Key Takeaways

  • Identify the reasons behind third brake light failure, such as burned-out or faulty bulbs and LED problems
  • Troubleshoot the issue by checking power, ground connections, fuses, and fuse boxes
  • Seek professional mechanic assistance or opt for brake light assembly replacement, if needed

Understanding the Third Brake Light

The third brake light, also known as the center high mount stop lamp (CHMSL), is an important safety feature in your vehicle.

This extra light provides additional visibility to other drivers, especially when your vehicle is obstructed due to road conditions or vehicle height.

When the third brake light stops working, it can be a cause for concern. Here are some common reasons and solutions to help you troubleshoot:

  • Burned-out bulb: The most common reason for a third brake light not working is a burned-out bulb. Replacing the bulb is typically an easy fix, and you can do it on your own or ask someone to help.
  • Faulty wiring: Another possible cause is faulty wiring. If the electrical wiring connecting the third brake light to the brake system is damaged or disconnected, it will not function properly. In such cases, you might need professional assistance.
  • Blown fuse: A blown fuse can also cause your third brake light to stop working. Check the fuse box (usually located under the dashboard or in the engine compartment) and replace the blown fuse with one of the same resistance.
  • Bad socket: If the bulb itself is in good condition, but the third brake light is still not working, the issue might lie in the socket. Inspect the socket for any signs of damage or corrosion and replace it if necessary.
  • Malfunctioning turn-signal switch: If your brake lights are not working but your third brake light is, the problem could be a malfunctioning turn-signal switch. You might need a mechanic to diagnose and fix this issue.

It’s crucial to ensure that your third brake light is functioning correctly, as it contributes significantly to your vehicle’s safety on the road. Don’t hesitate to address any issues and maintain your vehicle in excellent condition.

Common Causes of Third Brake Light Failure

When your third brake light is not working, some common causes could be a faulty bulb, wiring issue, bad fuse, or short circuit. Let’s discuss these in brief.

A faulty bulb is one of the primary reasons for a non-functioning third brake light. In this case, you should check the bulb and replace it if needed. This can usually be done by opening the trunk and accessing the brake light.

Wiring issues can also cause your third brake light not to work. If a broken wire or corroded connection is preventing the electricity from reaching the brake light, you may need to fix or replace the wiring.

Bad fuses and blown fuses often result in a non-functioning third brake light. You should inspect your vehicle’s fuse box and replace any damaged fuses. Remember, fuses play a vital role in the vehicle’s electrical system and help prevent short circuits.

Speaking of short circuits and open circuits, they are common electrical issues that can disrupt the functioning of the third brake light. Addressing these problems requires careful inspection of the vehicle’s wiring and connections.

Corrosion can affect the bulb sockets, connectors, or even fuse box, leading to the third brake light not working. Regular maintenance and cleaning can help prevent corrosion.

A faulty brake light switch can also be responsible for the malfunctioning of the third brake light. This switch connects the brake lights to the brake pedal, so replacing or fixing it is essential to get your brake light working again.

It’s crucial to address the issues mentioned above, as a non-functioning third brake light can impair the safety of your vehicle, putting you and others at risk.

Faulty Bulb and LED Problems

When a third brake light stops working, it’s often due to a faulty bulb or LED. Burned-out bulbs can be easily identified by checking the filament to see if it’s blackened or broken.

To replace the bulb, first access it, usually through the car trunk for most cars. However, refer to your user manual to learn how to access it. Once you’ve removed the burned bulb, simply replace it with a new one.

LED brake lights can have similar issues. You can use an LED test light to check for any problems with the LEDs.

These lights are known for their longevity, but they’re not immune to failure. Faulty LEDs should also be replaced to restore the functionality of your third brake light.

Some common causes of faulty bulbs or LEDs include:

  • Burned-out bulb or LED
  • Damaged filament in the bulb
  • Incorrectly installed bulb or LED

Comparing bulbs and LEDs, both have their pros and cons.

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Remember, it’s essential to diagnose the issue before changing out the bulb or LED. This will help you avoid unnecessary expenses and ensure the problem is fixed with the first attempt.

Diagnosing Brake Light Issues

When diagnosing brake light issues, it’s essential to start by checking if the problem is exclusive to the third brake light or if all brake lights are affected. Begin your diagnosis by inspecting the bulbs and fuses.

Inspect the bulbs: Remove the cover from the affected third brake light and check the bulb for any visible damage. If it appears burned out or damaged, replace it.

Test the fuses: Locate your vehicle’s fuse box, usually under the hood or inside the passenger compartment. Identify the brake light fuse and use a test light or continuity tester to see if it’s blown. If it is, replace the fuse.

If those initial checks don’t resolve the issue, you might need to test the third brake light circuit and brake booster.

Use a test light or LED test light: Connect the test light to a good ground on your vehicle and probe the brake light circuit at the third brake light connector. If there’s no power, the issue may be with the wiring or brake light switch.

Test the brake booster: Verify that the brake booster is functioning properly. If the booster is malfunctioning, it may affect your vehicle’s braking system, including the third brake light.

Additionally, digital sensors may play a role in diagnosing brake light issues, especially if your vehicle uses advanced systems for brake control.

As you diagnose brake light issues, remember the importance of accurate testing and thorough inspection. By following these steps, you can find and fix the problem with your third brake light in a friendly and efficient manner.

Power and Ground Problems

When your third brake light isn’t working, there could be issues related to power and ground in your car’s electrical system.

Let’s dive into these issues and give you some advice on how to tackle them.

Faulty Wiring Connections

Your third brake light might not be working if there’s a wiring issue in your car. Wiring problems can occur due to corrosion, damage, or disconnected wires.

To identify such issues, examine the wiring diagram of your vehicle to locate the power and ground wires for the third brake light. If you spot a disconnected or damaged wire, reconnect or repair it to fix the problem.

For example, imagine you’ve found that the ground wire is disconnected from its designated spot. You can simply reconnect it, and your third brake light might start functioning correctly.

Blown Fuses

Another reason for power-related problems that can cause your third brake light to stop working might be a blown fuse. If a fuse is blown, the power supply to the third brake light could be interrupted.

To resolve this issue, locate and inspect the fuse related to the brake lights in your car’s fuse box. If it’s blown, replace it with a new one with the same amperage rating.

Remember, the fuse box location can differ depending on your vehicle’s make and model. Consult your car’s manual if you’re unsure where to find it.

Bad Ground Connections

A poor ground connection can be another possible cause for your third brake light not working. In this case, inspect the ground wire’s connection point.

If it’s rusty or corroded, clean it with a wire brush and reattach it. You might also consider replacing the ground wire if it’s damaged.

By addressing power and ground problems in your car, you should be able to resolve any issues with your third brake light. Good luck, and stay safe on the road!

Fuse and Fuse Box Related Troubles

When your third brake light stops working, first check the fuse box to see if there’s a blown fuse. Fuses are responsible for protecting the electrical circuits in your vehicle, and if one is blown, it could cause the brake light to malfunction.

To locate your vehicle’s fuse box, check your owner’s manual. Once you’ve found it, look for the brake light fuses and inspect them. If you notice a bad fuse, replace it with a new one of the same type and rating.

If you’re unsure of the fuse location, the owner’s manual should have a diagram that identifies the specific fuse for the third brake light. Keep in mind that there might be more than one fuse box in some vehicles, so be sure to check all of them.

In some cases, your vehicle may have a bad fuse that still looks good from the outside. To diagnose this issue, use a multimeter to test if the fuses are working correctly. If the multimeter confirms a fuse is bad, replace it.

Remember, if you continue to encounter problems with your third brake light even after checking and replacing fuses, consider consulting a professional mechanic for further assistance.

Professional Assistance

When dealing with a third brake light that’s not working, seeking professional help is always a good option.

Your friendly mechanic will have the skills and tools necessary to diagnose the issue effectively.

They’ll start by checking the brake pedal switch, which is a common cause of third brake light problems. This switch sends a signal to illuminate the brake lights whenever the brake pedal is depressed.

It can become faulty or disconnected over time, resulting in a non-functional third brake light. If this is the issue, your mechanic will replace or reconnect the switch, depending on the circumstances.

Another issue could lie with the connector, harness, or bulb connector. This can result from wear and tear, corrosion, or a damaged wire. Again, your mechanic will be skilled in analyzing these connectors and harnesses to find the source of the problem.

They’ll replace or repair any problematic components, ensuring your third brake light functions as expected.

In some vehicles, the third brake light is connected to the turn signal switch. This can lead to the third brake light failing to work if there’s an issue with the turn signal switch. Your mechanic can check for possible problems and repair or replace the switch if necessary.

Keep in mind, professional assistance is not just limited to mechanics. Many dealerships offer repair services for their respective vehicles, and they might have more specialized knowledge on your specific make and model.

In conclusion, seeking professional assistance from mechanics or dealerships can save you time and trouble when resolving your third brake light issues.

They have the expertise to identify and solve the problem quickly, ensuring your vehicle’s safety on the road.

Brake Light Assembly Replacement

Replacing the brake light assembly is a straightforward process. First, you need to identify the cause of the non-functional third brake light. Common reasons include a burned-out bulb, broken wires, or a malfunctioning brake light switch.

To replace the bulb, follow these steps:

  1. Locate the third brake light assembly, usually found on the rear window or the trunk spoiler.
  2. Remove the cover or any screws holding the assembly in place.
  3. Carefully take out the old bulb and replace it with a new one.
  4. Reattach the cover or screws and test the brake light to ensure it’s functioning properly.

If your Silverado third brake light isn’t working, you may need to check for broken wires. Inspect the wiring connected to the assembly for any damages.

If you find broken or frayed wires, you can repair them using electrical tape, wire connectors, or soldering.

If the bulb and wiring appear intact, the issue could be related to the brake light switch, which is typically located near the brake pedal. If you find the switch is faulty, you may need to replace it.

For complex problems, consider seeking professional help as some issues may require specialized tools or expertise.

Keep in mind that functioning brake lights, including third brake lights, are crucial for road safety, alerting other drivers when you’re slowing down.

Additionally, emergency flashers use the same bulbs as brake lights, so fixing the third brake light also ensures proper functioning of emergency flashers.


In conclusion, when your third brake light stops working, it’s crucial to address the issue promptly for your safety and those around you. Typically, the problem can be attributed to a few common causes:

  • Burned-out bulb: A simple and common issue, you can easily replace the bulb yourself or seek assistance from a friend.
  • Blown fuse: Check your vehicle’s fuse box and replace any blown fuses accordingly.
  • Wiring issues: Malfunctioning or damaged wiring may require the expertise of a mechanic for proper diagnosis and repair.
  • Bad socket and connectors: Inspecting and cleaning or replacing faulty sockets and connectors can resolve the issue.
  • Grounding issues: A mechanic can help diagnose and repair any grounding issues affecting the third brake light.
  • Faulty brake light switch: Replacing the brake light switch may be necessary to restore functionality to your third brake light.

Remember, the sooner you address a non-working third brake light, the safer you’ll be on the road. Don’t hesitate to consult a mechanic if you’re unsure about your diagnosis or if the problem persists after trying these solutions.

Frequently Asked Questions

What could cause a 3rd brake light failure?

A third brake light failure could be caused by a burned-out bulb, a blown fuse, a bad socket, or even a faulty brake switch. If you notice your third brake light not working, it’s crucial to resolve the issue as soon as possible to maintain proper road safety.

How to check the fuse for the third brake light?

To check the fuse for your third brake light, locate your vehicle’s fuse box, and use the fuse diagram on the box’s cover or in the manual to find the brake circuit fuse. If you find the fuse has blown, simply replace it with a new fuse of the same resistance.

Is there a specific third brake light fuse location?

The third brake light fuse location varies depending on your vehicle’s make and model. Generally, the fuse box can be found in one of two locations: inside the cabin or beneath the hood. Consult your vehicle’s manual or a professional mechanic for the exact location.

How to determine if a brake switch is causing the issue?

To determine if a brake switch is causing the issue, locate the brake switch near the brake pedal. Disconnect the wiring harness, and use a multimeter to check for continuity. If you find no continuity when the brake pedal is pressed, the brake switch might be faulty and needs to be replaced.

What are some common troubleshooting steps for brake light problems?

Common troubleshooting steps for brake light problems include:

  • Checking for burned-out bulbs and replacing them if needed
  • Inspecting the fuse and replacing it if it’s blown
  • Examining the socket for any signs of damage or corrosion
  • Testing the brake switch for proper functionality

How important is fixing the third brake light?

Fixing the third brake light is crucial for your safety and the safety of others on the road. This light increases the visibility of your vehicle when braking, helping prevent rear-end collisions.

Moreover, operating a vehicle with a non-functioning third brake light could lead to traffic citations or even accidents. It’s always best to address any brake light issues promptly.

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Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

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