Blog Car Care Advice Tail Lights Not Working But Brake Lights Are? (6 Reasons Why)
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Tail Lights Not Working But Brake Lights Are? (6 Reasons Why)

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Are your tail lights not working but brake lights are?

The rear lights of a vehicle — your tail lights and brake lights — work in unison to improve road safety. But, sometimes, you may find that the tail lights aren’t working when the brake lights are.

What causes tail light issues?

In this article, we’ll examine why your tail lights aren’t working but brake lights are, including possible diagnostic steps and remedies. We’ll also explore some FAQs about brake lights and tail lights.

This Article Contains

Let’s get started. 

Tail Lights Not Working but Brake Lights Are? 6 Potential Causes (Plus How to Diagnose and Fix Them)

Brake lights and tail lights are interlinked, often sharing the same light bulb in some cars. But while tail light and brake light issues are similar, their root causes may differ.

Here are potential reasons behind tail lights not working:

1. Faulty Turn Signal Switch

The turn signal switch (or headlight switch) is a lever on the steering column’s side managed by the body control module. 

The turn signal switch sends an electrical signal that activates a vehicle’s light systems, like headlights, taillights, and parking lights.

When the turn signal switch is faulty, it cannot send an electrical signal to the head light and tail light. The taillights won’t turn on without the electric signal from the light switch. 

How to diagnose:

How to fix: 

  1. Remove the column shroud by loosening the screws around the light switch.
  2. Use a screwdriver to disconnect the light switch.
  3. Attach the new light switch to the cables.
  4. Test the turn signal switch by flipping it to different modes to see if the tail lights work.
  5. Reattach the shroud back onto the steering column.

2. Blown Fuse

A car fuse safeguards the tail light and brake light circuit from overcurrent.

However, a high electric load on the rear light can cause a blown fuse and the tail light to stop working. This malfunction could happen even if you still have a working brake light.

How to diagnose:

How to fix:

A mechanic would pull the fuse from the box and read the resistance markings on its side. Once they identify the resistance specifications, they’ll add an appropriate replacement.

3. Bad Tail Light Bulb

Car manufacturers use a specific type of light bulb to fit their designs. Some cars have LED bulbs, while others may have xenon or halo light bulb installations.

Generally, the brake light and tail light use the same dual filament bulb. So, if one of the filaments in the light bulb breaks, the tail light may stop working while the brake light still works.

However, some manufacturers use a separate light bulb for the brake light and tail light. This separation makes detecting a bad tail light bulb simpler.

How to diagnose:

The ideal method to detect a faulty tail light or brake light bulb is to check its filament. 
The filament in the taillight bulb creates illumination but cannot do so when broken. 

How to fix:

If you suspect the tail light or brake light bulb has a broken filament, contact a mechanic who can help you replace the light bulb.

They would:

  1. Locate the rear light housing on the door of your car’s boot.
  2. Remove the boot interior to access the light socket and light bulb.
  3. Remove the old light and replace the taillight bulb depending on your required type (Xenon, Halogen, or LED bulbs).
  4. Test the taillights and mount the light socket back in its place.

4. Faulty Light Socket

The rear tail light socket holds the light bulb and connects it to the light circuit. 

When the taillights of a vehicle aren’t appropriately sealed with silicone, they can be exposed to wind, dust, and water. This exposure mainly affects the rear tail light socket, which is more prone to rust and corrosion.

Why does this matter?
Any damage to the light socket means it cannot carry the electric current from the battery to the tail light, leading to complications.

How to diagnose:
If the light bulb and fuse are in good condition, the issue may be with the light socket.

Here’s what a mechanic would do to confirm a light socket issue:

How to fix it:
Like a light bulb, the light socket must be replaced if it’s in poor condition.

Here’s how:

  1. Find the tail light housing on the door of the boot.
  2. Remove the boot upholstery to access the light socket and light bulb.
  3. Disconnect the power cable and remove the old light socket.
  4. Replace the worn-out light socket with a new one.
  5. Reconnect the power cable to the light socket and check if the tail lights work now.

5. Faulty Wiring or a Bad Electrical Ground

A car’s wiring distributes power from the battery to other components, such as the dash lights, reverse lights, the 3rd brake light, and tail lights. The wiring prevents the electric load from cross-feeding crucial car parts (whereby you switch on the headlights, but the reverse lights turn on).

But here’s the thing:
If the light socket and fuse are in good condition, your tail light issue may stem from faulty wiring or a damaged electrical ground wire.

Faulty wiring or corroded ground wire can’t prevent the electric current from cross-feeding the different components. That’s why you may find that your dash lights, reverse lights, and brake lights work while your taillights don’t.

How to diagnose:
Diagnosing circuit issues can be complex, so get a hold of a mechanic if you’re not sure how. 
They would: 

How to fix:
A mechanic can remove the damaged part of the wiring and retwist it for better circulation. They would also realign the entire wiring system to prevent cross-feeding.

6. Damaged Ambient Light Sensor

Newer car models have automated headlights and taillights configured by an ambient sensor. 

The car’s in-built sensor helps detect dimness outside, which switches lights on accordingly. The sensor also controls the license plate light, parking light, and daytime running light. The parking light helps with driving at night and the running light assists in daytime driving. 

So, a damaged ambient light sensor may result in your head light and tail light not working correctly, reducing safety. Moreover, your parking light and the running light may also malfunction.

How to diagnose: 
If your ambient light sensor is damaged, it cannot accurately read outside temperatures. This inaccuracy manifests as inconsistent or faulty lighting, whether it’s the tail lights, headlights, or any other lights.

How to fix:
A faulty ambient light sensor needs a replacement. Contact a professional who can assist you with erratic car lighting.

Now, let’s explore more about tail lights and brake lights.

3 FAQs About Tail Lights and Brake Lights

Here are answers to common queries you may have about tail lights and brake lights:

1. What’s the Difference Between Brake Lights and Tail Lights?

The difference between the brake light and the tail light lies in their purpose and design.

A working brake light illuminates when you apply pressure to the brake pedal and alerts other drivers that you’re slowing down. When the brake pedal is depressed, the brake light switch is released. The release of the brake light switch completes the brake light circuit, and activates the lights.

When the brake pedal returns to its original position after braking, the brake pedal touches the brake light switch and turns the brake light off. 

With taillights, it is much simpler. The driver switches on the headlight switch, which relays an electrical signal to both the headlight and tail light for better visibility.

2. Why Are My Brake Lights Not Working But My Tail Lights Are?

As you apply pressure to your brake pedal, you may notice that your brake light is malfunctioning while your taillights aren’t.

Here are potential reasons why:

3. Can You Drive Without Working Tail or Brake Lights?

Traveling with damaged or defective tail lights and brake lights is considered a traffic violation. Driving without proper tail lights, brake lights (even a 3rd brake light), and headlights pose a severe safety risk to you, your passengers, and others on the road.

Closing Thoughts

There are several reasons why your tail lights aren’t working, including a bad light bulb, damaged fuse, and corroded light socket. 

While you could try to solve the problem yourself, it’s better to leave it to professional mechanics like AutoNation Mobile Service.

AutoNation Mobile Service is a convenient mobile auto repair and maintenance solution offering competitive, upfront pricing. Fill out this form for an accurate cost estimate for brake light and tail light repair! Our expert mechanics will fix your brake and tail lights right from your driveway.