What Is a Brake Light Switch and When Should You Replace It?

The brake light switch on your vehicle serves an important safety function. When you press the brake pedal, it supplies power to the signal lights at the back of your vehicle to warn other drivers you have slowed.

“If this switch starts to fail, you might notice a few warning signs,” says Duane “Doc” Watson, a technical trainer at Bosch Mobility Aftermarket. “The brake lights don’t come on when you press the pedal; they stay on even when you’re not braking, your cruise control stops working correctly, or you can’t shift out of park easily.”

Over time, they can fail from wear or electrical issues. If you suspect your brake light switch is faulty and needs to be replaced, here is how to find it and diagnose whether that’s the problem.

Where is a Brake Light Switch Located?

As part of the brake-pedal assembly, you can find this switch under the dashboard or on the firewall near the top of the pedal lever. Replacing one is easy.

Once driven by hydraulic pressure in the brake line (a system prone to failure), vehicle manufacturers transitioned to the more reliable mechanical brake light switch by the end of the 1960s. Now, it is rare for a switch to fail. Current designs employ a relay, allowing a lower-voltage control circuit to operate the main power supply switch for the brake lights. This configuration creates a reliable switching mechanism with a long lifespan.

How Do You Know if Your Brake Light Switch is Bad? Diagnosing the Problem

You won’t get much warning before a brake light switch fails— at most, you’ll see some flickering or inconsistency in light stability. More likely, the brake lights just stop working.

Chances are, someone else has alerted you to the issue. Check for yourself at night. Looking through your side mirror. Light intensity should increase behind the vehicle as you engage the brake. Alternatively, you can back up to a wall or garage door, put the car in park and watch through the rear-view mirror as you engage the brake.

Broken Brake Light?

Identify a faulty brake light switch through a process of elimination. Check the light bulbs for cracks or broken filaments. Make sure the bulbs and wiring harnesses are connected and seated tightly. Did both lights fail at the same time? If so, a bad switch is more likely.

How Much Does it Cost to Replace the Brake Light Switch?

A replacement brake light switch generally costs around $30 to $75, depending on the make and model of the vehicle. Getting a brake light switch fixed at a shop will add typically $80 to the repair.

Learn the things you should never do to your car in the video below.

FAQ

How long does it take to replace a brake light switch?

It usually takes between 10 and 30 minutes, depending on the vehicle.

“It’s typically accessible beneath the dashboard near the brake pedal, and if so, that requires minimal tools,” says Kevin Oliff, general manager at AutoNation BMW Buena Park. However, due to its impact on safety, if you don’t feel comfortable replacing it, Oliff recommends taking it to a professional.

Will replacing the brake light switch fix all brake light issues?

Not necessarily. It can solve the lights not turning on when the pedal is pushed, the cruise control not working properly and difficulties switching out of park, but it won’t solve problems caused by burnt-out brake light bulbs, faulty wiring, poor electrical connections or blown fuses, says Watson.

“If none of your brake lights are working, the brake light switch might be to blame,” says Watson. “If only one side is working, it’s likely a bulb that needs to be replaced. You can also check the bulbs for cloudy glass or if the small wire inside, the filament is burned out.”

About the Experts

• Duane “Doc” Watson is a technical trainer at Bosch Mobility Aftermarket. He has more than 45 years of experience in automotive repair, has trained thousands of technicians and earned many industry awards, including Chevrolet Technician of the Year and Buick Service Master of the Year.
• Kevin Oliff is the general manager at AutoNation BMW Buena Park in California and has more than 20 years of experience in the automotive field.