Third Brake Light Not Working

Third Brake Light Not Working: Possible Reasons and Solutions

Since 1974, when psychologist John Voevodosky tested the third light, it has been a crucial vehicle gadget. It helps the drivers know when they brake the vehicle, preventing rear-end collisions. But sometimes, the third brake light may stop working.

So, why is the third brake light not working? Some reasons the third brake light may stop working include a blown fuse, a burned bulb, or wiring issues. To be sure of the failing part, diagnose each cause further. You can do the repair work or hire a professional.

Driving without the third brake light can be hazardous and needs immediate fixing. Read on to learn the possible reasons why this light may not be working and the solutions.

Reason Why Third Brake Light Not Working: Diagnose and Fix

Some of the reasons these lights may stop working include;

Reason Why Third Brake Light Not Working

1. Burned Bulbs or LEDs

Burned bulbs or LEDs are common reasons the third brake light may fail. Most brake lights have a lifespan between 250 and 700 hours or about four years of use. However, most modern vehicles that use LEDs have a longer lifespan.


To be sure the burned bulb or LED is the reason the third brake light is not working, perform a diagnosis.

  1. Access the bulb, usually through the car trunks for most cars. However, refer to the user manual to learn how to access it.
  2. Check the bulb’s filament to see if it’s blackened or broken.
  3. Check the bulb if it’s broken.
  4. Access the LED and disconnect its socket.
  5. Test the socket for power. The LED may be faulty if there’s some power.
Burned Bulbs or LEDs


Replace the bulb if your diagnosis shows that the bulb is bad. Follow the steps below.

Step 1. Depending on the vehicle’s model, you may need to open its trunk.

Step 2. Access the brake light. In some vehicles, it’s attached to the trunk, and in this case, removes the cover to access the light. Also, in some models, it is fitted on the vehicle’s roof.

Step 3. Unplug the brake light socket.

Step 4. Unscrew the brake light from the vehicle. On some models, you unscrew the bulb holder. For an on-roof car model, you start with unscrewing and then unplugging the socket.

Step 5. Install a new third brake light.

Step 6. Screw it back on and plug back the socket.

A mechanic will cost you between $100 and $200 to replace the rear third brake light.

2. Blown Fuse

Like most electrical devices, the third brake light and the other two brake lights have a fuse that protects them from excessive current. A blown fuse can be a reason the third brake light may not be working when other brake lights do. The fuse blows due to a current overload.


Brake light fuses are usually in the fuse box, under the hood or kick pane on the passenger side’s compartment. However, consult the user manual to learn the location of the fuse box.

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To confirm whether the fuse is the reason the third brake light is not working, perform these diagnoses.

  1. Locate the fuse box.
  2. Consult the diagram, usually in the fuse box, to locate the third brake light fuse.
  3. Remove and check the fuse. It should appear burnt.
  4. You can also use the test light by connecting it to the car battery’s negative and touching the fuse’s probe.
  5. Also, you can use a digital multimeter by connecting its negative to the car’s battery and the positive one to the fuse’s probe.
Car Blown Fuse


Once you have confirmed the fuse is the problem, replace it. Buy a compatible fuse that is identical to the one already installed. Consult the user manual for the fuse amperage and type. Follow the steps below to change it;

  • Step 1. Turn off the vehicle.
  • Step 2. Locate the fuse box.
  • Step 3. Consult the user’s manual to know which is the third brake light.
  • Step 4. Pull out the blown third brake light fuse using a fuse puller or needle-nose pliers.
  • Step 5. Insert the new fuse and ensure it fits securely.
  • Step 6. Test the third brake light by having someone depress the brake pedal while you watch it.

Fixing a blown fuse problem can cost between $50 and $130.

3. Wiring Issues

Another possible reason the third light may not be working is wiring issues. The wiring to the third light may be broken or faulty, causing the light not to work when you press the brakes.

In most vehicles, the third brake light is wired separately to avoid failure, which is why the others may still work. Wires often become damaged after years of the door being opened and shut.


To confirm the wiring issues are causing the third brake light not to function properly, perform further diagnosis.

  1. Access the wiring to the third brake light
  2. Analyze the wire loom for damage
  3. Check the state of the sockets and harness
  4. Check for signs of damage on any exposed wiring
  5. Check for flayed wires too
  6. Pull out the socket from the lamp and test for voltage
Third Brake Light Wiring Issues


The wiring must be changed if the wires are damaged, and there’s no voltage to the third brake light. In most models, the wiring to the third light involves a harness. Follow the steps below;

  • Step 1. Access the wiring harness to the third brake light
  • Step 2. Detach sockets from the brake light
  •  Step 3. Unplug the harness from the main wiring
  • Step 4. Plug in a new harness
  • Step 5. Attach sockets from the new harness to the third brake lights

A mechanic will cost between $75 and $250 to replace the third brake light. The cost varies with the car’s model and repair shop.

4. Corroded Contacts

The sockets that connect the third brake light to the wiring or harness can get corroded. Corrosion can happen if the contacts were initially loosely installed, allowing water to creep in. In this case, this light may not receive the electrical signal when the brake pedal is depressed.

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Diagnose by checking the third brake light’s socket to determine whether they are the reasons behind the issue. If the socket’s contacts appear corroded, they may be the reason.

Third Brake Light Corroded Contacts


Some of the solutions to corroded sockets include;

1) Cleaning

One of the solutions is to clean the socket. A Q-tip or a micro file are some of the things that can be used to clean corroded sockets.

2) Replacing

Replace the socket if it is badly corroded and cannot be washed. Buy a new compatible socket and install it in the place of the old one.

If you’re grappling with a non-functional third brake light, our article on can you pass inspection with ABS light on might provide insights on resolving related concerns. Furthermore, if you’re a Subaru Forester owner and facing ABS-related challenges, our guide on Subaru Forester ABS light on issues is here to assist you. We recognize the importance of maintaining vehicle safety and compliance, and our comprehensive resources are designed to help you troubleshoot and address any issues you might encounter.


Some related questions in this section should help answer some of your queries.

Q1. Can Bad Brake Light Switch Cause the Third Brake Light Not to Work?

Yes. When the brake light switch is faulty, usually no brake light comes on when the brake pedal is depressed. There is no current past the switch when it has issues, meaning no lights are on. However, if other brake lights are off too, it may be a cause.

Q2. Can I Drive with a Faulty Third Brake Light?

You should not drive with a faulty third brake light as it can be dangerous. The light helps keep you safe by notifying drivers behind you when you brake or stop. However, if the other brake lights are working, you can drive, but only towards a repair shop to get it fixed.

Q3. How Long Does it Take to Diagnose and Repair a Faulty Third Brake Light?

Most repair shops can get the faulty third brake light replaced within an hour. The car’s model heavily determines the time since some don’t require you to remove any car parts. However, some vehicles may take longer, especially if there are other problems too, like damaged or corroded harnesses.

Bottom Line

The third brake light is a crucial safety feature, among the reasons it is a big deal when it is not working. The light may fail to work for various reasons, including faulty wiring, bad fuse, or corroded socket contact. To be sure which part is failing, diagnose the possible cause further.

Fixing the problems causing the third brake light not to work is easy by following the steps discussed in the article. Contact a mechanic for further diagnosis and repair if you’re uncomfortable doing it.

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