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

The brake light switch on your vehicle serves an important safety function. Learn how to test it and determine when to 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.

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.

What should I do when the brake warning light comes on?

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.

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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, possibly some flickering or inconsistency in light stability. Most 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.

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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.

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