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Brake Lights Not Working: 5 Typical Causes + How to Diagnose

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Brake lights not working?
It might be a good idea to get them replaced.

Tail lights and brake lights are located at your vehicle’s rear. 

Tail lights activate when the headlight switch is turned on. On the other hand, the brake light illuminates when your press the brake pedal — telling other drivers that you’re slowing or have stopped.

Working tail lights and brake lights help prevent accidents, and keep you from getting a traffic ticket. So, you can imagine what happens if they don’t. 

In this article, we’ll explore five common reasons behind a brake light problem and some risks associated with broken brake lights. We’ll also tell you how to diagnose malfunctioning brake lights and answer some FAQs.

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Let’s get started.

Why Are My Brake Lights Not Working? (5 Common Causes)

Like any other light bulb, a headlight, brake light or tail light bulb can fuse or malfunction. Although brake lights last long, certain conditions can cause your brake light system to fail sooner. 

Here are five common bad brake light instigators:

1. Bad Bulbs

There are several lightbulbs underneath each tail light lens. One of them is the brake light bulb.

The first and most common cause of brake light failure is a blown-out light bulb, mostly observed in older vehicles. Newer models have LED lights installed in the tail light and headlight assembly, and these last significantly longer.

If you press the brake pedal and your brake lights (red in color) don’t light up, you should suspect a bad brake light bulb. Turn on your tail lights to see if the issue is isolated to the brake light, and not the entire tail light assembly.

Here’s how you can check for a blown brake light bulb:

If the light bulb has turned black or the filament is broken, it’s time to replace your brake lamp.

2. Bad Brake Light Switch 

The brake light switch is a simple on/off switch activated when you press the brake pedal.

If you notice a stuck brake light or your brake light doesn’t come on at all, there could be an issue with your brake light switch. 

Replacing this is fairly easy, but the process can vary depending on your car model. If you’re not sure how, it’s best to call a mechanic for a brake light switch replacement.      

3. Blown Fuse or Broken Fuse Box 

If your brake light switch works perfectly fine and yet the brake light doesn’t illuminate, you should check for a blown fuse or a broken fuse box. This is important because both these components affect the brake light circuit.

Here’s how:

If the fuse is blown, you’ll need to replace it with another fuse having the same resistance.

4. Bad Electrical Ground 

Another common cause of brake light malfunction is a bad electrical ground. In some vehicles, it’s also called switch-provided ground. 

If you haven’t observed any problems in your brake light switch, bulb, or brake light fuse, then a bad electrical ground might be why your brake light isn’t working. This can happen because of loose wire connections, corrosion, or damaged wire ends.

Here’s how to check for a bad electrical ground:

If the brake light illuminates, it means your existing electrical ground connection requires fixing.

5. Faulty Wiring 

If all the brake light components (light bulb, brake light switch, fuse, or fuse box) and electrical ground are working fine, the last thing you need to check for is faulty wiring.

Refer to the wiring diagram and carefully look at the wires connecting the fuse panel to the brake light switch. Also, check the wires connecting the brake light switch to the bulb. 

If you observe a broken brake wiring harness, loose or frayed connections, or signs of corrosion on the bulb housing, it indicates that your brake light needs replacement.

What are the risks associated with a faulty brake light?

Risks of Driving with Broken Brake Lights

Cars brake lights and taillights are essential safety features to help prevent vehicle collision. Driving with faulty rear lights can be very dangerous.

Here are some risks of driving with a broken brake light:

1. High Chances of Accidents 

Illuminating rear brake lights indicate to other vehicles that your car is slowing down. If your rear lights or tail lights aren’t working correctly, those behind you won’t get the signal, and you could get rear-ended.

2. Shifting Problems 

When your car’s brake lights go out, it can activate your car’s shift lock override. 

The shift lock override prevents your car from shifting in case mechanical errors are detected. As such, driving with broken brake lights can damage your vehicle’s transmission system. To avoid these issues, consider installing a 3rd brake light.

3. Danger During Harsh Weather 

Driving during rainstorms, whiteouts, or intense fog, can increase your chances of getting into a collisions. In conditions with extremely low visibility, rear brake lights and tail lights are your vehicle’s only brake components visible to other drivers.

If you are driving with a broken brake light, other drivers won’t know if you are slowing down or stopping.

Let’s check out how a mechanic will diagnose your brake light problem.

How to Diagnose Malfunctioning Brake Lights?

While brake light components vary from vehicle to vehicle, here are the basic steps a mechanic will take to diagnose broken lights:

Step 1: Check the Bulb and Fuses 

They’ll check the bulb and fuse connected to the brake switch, turn signal switch, and tail light. 

Many new cars have one light bulb per tail light with two filaments — one for the brake light and one for the turn signal. If the brake pedal is pressed and your turn signal is engaged, the already-illuminated bulb starts to turn on and off. 

Likewise, the brake light circuit is also connected to the turn signal circuit. This means that the brake light will not come on if the turn signal switch is damaged. 

Your mechanic will locate the wire connecting the turn signal switch and brake light switch. Next, they’ll backprobe the wire with a test light to check both switches. They’ll replace the wire if the test light doesn’t come on.

Step 2: Check the Bulb Sockets

Next, they’ll check the bulb or the light socket for any sign of corrosion or melted plastic and ensure that the bulb socket is clean. 

Many times, a brake light issue arises due to bad bulb sockets. Your mechanic may clean the bulb socket with a Q-tip, micro file, or sandpaper. 

Step 3: Check Ground and Voltage

If the light bulb sockets aren’t the problem, your mechanic will check the ground and voltage connection. When you press the brake pedal, they’ll measure the voltage at the taillight and test the brake pedal switch.

The vehicle’s wiring diagram will help them identify the ground points and which wire provides the 12V battery voltage to the brake light.  

Once the ground points are located, they’ll test the socket pins. If there’s no voltage in the socket, they’ll check the 12V wire with a multimeter. Next, they’ll test the ground on the continuity setting.

If the ground is good, your mechanic might still loosen the ground bolt to clean the terminal and re-install it. If not, they’ll replace it.

Still have questions about the brake lamp?
We’ve got the answers.

4 FAQs on Brake Lights 

Here are answers to some of the most commonly asked questions:

1. How Much Does It Cost to Replace a Brake Light?

The price of the brake light bulb can vary from $5 to $10, and the mechanic might charge around $20 for labor. The maximum charge for getting the replacement could be around $30.

2. How Long Does It Take to Replace a Brake Light?

It takes about 40 minutes for a brake light replacement. At max, a mechanic will take an hour to complete the job. 

3. How Long Do Brake Light Bulbs Last?

Brake light bulbs can last up to 4 years or 40,000 miles. But they may go bad sooner, depending on driving conditions, such as excessive braking in stop-and-go traffic. However, newer car models use LED lights in their tail light and a headlight that last longer. 

Always use a high-quality replacement brake light bulb to ensure your brake lights operate efficiently.

4. Can I Drive With No Brake Lights?

It is not advisable to drive with malfunctioning brake lights or tail lights as it increases the risk of accidents, especially in low visibility conditions.

Even if you have a single brake light out, you can get pulled over by the authorities. For this, you may only get a verbal warning. However, driving with more than one failed brake light, tail light, or headlight is against the law, and you’ll likely receive a ticket.

Wrapping Up 

Faulty brake and tail lights can increase the risk of road accidents and threaten the lives of other drivers and passengers. As such, you shouldn’t wait to get the problem fixed.

Want your brake light issue resolved right in your driveway?
Contact AutoNation Mobile Service.

AutoNation Mobile Service is a mobile car repair and maintenance solution that offers you:

Get in touch with us for easy replacement of your brake light, parking light, daytime running light, headlight or tail lights and for any other car repair service.