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Bad Brake Light Switch Symptoms & Replacement

CarPart  ·  April 28, 2023

Bad Brake Light Switch Symptoms & Replacement

The brake light switch is somewhat unknown to most drivers, even though they use it every time they step on the brake pedal. As the name suggests, the switch activates the brake lights whenever the driver slows the vehicle down or brings it to a halt.

The symptoms of a bad brake light include (1) brake lights won’t turn on, (2) staying lit when they shouldn’t (3) malfunction/issues with stability, cruise control, and braking systems, (4) car won’t start, and (5) dashboard warnings.

With this short article, you'll learn all about the brake light switch in your car. You'll discover what it does, where to find it, and what happens when it goes wrong. Lastly, you'll learn a few things about replacing a bad switch with a new one.

Let’s get started!

What Is a Brake Light Switch?

The brake pedal switch is just one of countless switches, sensors, and other electrical or electronic components in your car. Because of that, it’s worth revisiting what the brake light switch is, what it does, and how it works.

The brake light switch is exactly as the name suggests: it activates the brake lights on your car's rear for the attention of other drivers. Unlike the other buttons you control with your hands, the brake light switch is controlled by your foot.

That statement might be confusing initially, but it makes more sense when you ask, “Where is the brake light switch located?”

The brake light switch is attached to your brake pedal. So, when you apply pressure to engage your vehicle’s brake system, you’re also activating the light switch that turns on the brake lights turn.

The brake light switch has multiple uses, particularly in newer car models. Aside from turning on the brake light, it also enables the push-button and gear selector shift in some car models.

On top of that, some car models connect that switch to the car’s stability control system and its anti-lock brake system (ABS). So, for example, stepping on the brakes will engage the brake switch sensor and cause the ABS hydraulic pump to start working.

Simply put, your actions when using the brake pedal are signalled to those systems with help from the brake light switch.

Whether you drive an older or newer model vehicle, there's no denying that the switch plays a critical role during your drive. So, it's worth learning the symptoms of a switch gone wrong and how to replace it.

How Do You Know If a Brake Light Switch Is Going Bad?

You can look for several symptoms suggesting your brake light switch is going bad or has failed completely. Those symptoms include:

1. Brake Lights Won't Turn On

As you read earlier, the primary function of the brake light switch is to activate the brake light when you step on the pedal. So naturally, the first sign that the switch has failed is when the brake lights won't turn on.

This symptom can be dangerous for you and other road users, as drivers behind you won’t know when you’re braking.

Unfortunately, most people won’t realise their brake lights aren’t turning on until it’s too late. That’s why you should test these lights when you take your car in for regular maintenance and servicing.

Alternatively, you get someone to help you test it at home occasionally. For example, a helper can step on the pedal while you see if the brake lights turn on.

2. Brake Lights Stay On

A brake light switch can also fail in the other direction, i.e. it could cause the brake lights to stay on even when they shouldn’t. This, too, is a dangerous condition that can confuse drivers on the road behind you.

Besides that, having the brake lights permanently turned on due to a bad switch will also cause it to burn out much sooner than usual.

On the plus side, this symptom is slightly easier to notice. For example, you might see your brake lights illuminating the space behind your car at night, even when you’re not stepping on the brake pedal.

3. Cruise Control Issues

Previously, you saw how the brake light switch is connected to other systems in new car models. One example is the cruise control system that typically disengages when brakes are applied.

Because of that, you’ll experience cruise control issues if the brake light switch is faulty. For instance, the cruise control feature might not work at all, or it might work only intermittently.

When troubleshooting cruise control issues, check the brake light switch as well.

4. Car Won’t Start

The brake light switch plays an additional role in cars with push-button starts. Starting a vehicle like that requires the driver to step on the brake pedal. Otherwise, the engine won’t start.

A bad brake light switch can disrupt that start procedure. For example, a problematic switch could fail to sense that you’re stepping on the brake pedal. As a result, it’ll prevent the engine from starting when you push the start button.

5. ABS Problems

Lastly, another symptom you’ll likely experience is a problem with the ABS system onboard. Typically, you’ll see the ABS warning light illuminate on your dashboard, telling you there’s a problem with the system.

Remember: There are plenty of different reasons for that light to turn on. However, if you’re troubleshooting the issue and can’t find a solution, it’s worth considering the brake light switch as a possible cause.

How Do You Replace a Brake Light Switch?

Technically, you can install a brake light switch or replace the existing one yourself. But given the importance of that switch and its connection to various systems, it's best to leave it to the professionals unless you have the skills and experience.

Whether you do it yourself or let a mechanic replace the faulty brake switch, the process typically involves these steps:

  1. Park the car on a flat surface and secure it to prevent rolling.
  2. Disconnect the car battery to avoid injury.
  3. Access the switch near the driver-side footwell, close to the brake pedal.
  4. Disconnect the brake light switch wiring harness.
  5. Remove the faulty brake light switch and install the replacement.
  6. Work backwards to reconnect the wire harness and then the car battery.
  7. Test the brake light switch to ensure it works correctly.

The process shouldn’t take much longer than other car repairs, especially since it happens inside the cabin and not under the hood. When done correctly, all systems connected to the switch will also function without any issues.

Looking for a compatible brake light switch? Check out CarpartAU for the new and used parts you need. You can browse the Marketplace to find deals on used parts or submit a request through the Parts Finder.


By Ray Hasbollah

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