Brake Lights Wont Work When Headlights Are On

What shall I do if my brake lights wont work when headlights are on? This can be a really big problem for night driving, and we have given you some ideas on what might be causing this problem.

If you’ve noticed that your brake lights don’t work when headlights are on, and your tail lights are on, it could mean a wiring issue. A faulty ground wire or broken circuit could cause this issue and can be easily corrected by an automotive electrician.

Some other causes of this problem may include: a defective headlight switch, failed brake light switch, water leakage into the driver’s side light control box (most common in older vehicles), burnt-out fuse for brake lights only.


Brake Lights Wont Work When Headlights Are On


The Main Reason Why Brake Lights Wont Work When Headlights Are On? A Broken Ground Circuit

If your tail lights are off but you press the brake, the electrical current will go through the brake lights but won’t be able to find the ground. It will then go to the front headlights instead to get ground there. 

Again, let us assume that the taillights are on. Now when you apply the brakes, both sides see a 12V current and since there is zero difference in the voltage, the bulb will again not work.

The problem is that the grounding wire for all the different brake light bulbs is spliced at one single joint. Then a single wire is connected to the central power console. It might be that this wire got corroded or broke some time back when you used scotch lock connectors for joining them. This is a common problem when you put in a trailer harness in your car.

Another possibility is that there has been damage to the wires running through the back of the car because a lot of people have been stepping in and out at the back.

Some other reasons are: wires might become dislodged, corroded, or completely ruined. Connect a good ground to the light switch. Make sure to test it with cables. 

Then, push the brake pedal to check that the brake lights are turned on. Is it switched on? The ground connection must then be replaced or repaired.


Brake Lights Wont Work When Headlights Are On


4 Reasons Why Your Brake Lights won’t Work But Your Headlights Do

#1 If the light bulbs are shattered

The brake lights are often not working because the light bulbs are blown out. These blown lights, I believe, are the most typical cause. What can be done about it? Unplug from the holder of the bulb. 

Turn the bulbs out of the socket counterclockwise after pressing the bulb’s switch. You can search the trunk for the precise place.

If the bulbs have discolored or blown filaments, you should replace them. Identical bulbs with the same features and power can be found on the market. If required, look them up on Amazon. The rear and brake lighting on some European cars are original specifications. Even though European bulbs have multiple filaments, you may readily replace them from a reputable retailer.

#2 Fuse boxes and light switches are sometimes responsible

Second, the light switch and fuse box should be kept in good working order if you want the brake lights to work correctly. You must first obtain the PDC to identify the reason behind brake lights malfunctioning (Power Distribution Center). The PDC is primarily found beneath the hood. 

Remove the brake light switch if it hits the rear brake arm and disturbs the light switch and fuse box, including the brake lights. Keep in mind that any issues with the fuse box or light switch will significantly impact the brake lights. You must replace them with new ones. The new bulbs should have the same ampere rating as the previous ones.


Brake Lights Wont Work When Headlights Are On


#3 Is the wiring system responsible for the failure of brake lights? 

Aside from examining the electrical ground, pay attention to the wiring! You should examine all of the elements we’ve discussed! It is vital to verify that they are in good operating order. Okay, we’ll have a look at the wiring system. Here’s where you’ll find the problem’s origins. The fuse panel that runs by the brake light switch may be loose. Furthermore, if the bulb socket and light regulators are torn, the bulb shell connection will corrode. It is advised that you replace these items as soon as feasible.

#4 In the end, check the ‘Turn Signal Switch’

We’ve worked on various car models, and our findings indicate that some vehicles have a connection between the brake light channel and the turn signal switch. 

If the brake lights don’t work when headlights are on, you will not receive any response. You can look at the switch’s wiring diagram to see how the brake light and turn signal are connected. 

To engage the light switch, go to the rotary light switches and look for the brake light’s activation source. If the brake pedal is pressed, check if the lights are turned on.

How to fix this problem?

You’ll need to isolate the end of the problem-causing wire to correct this problem. It may be a ground, signal, or power wire. You can do this by taking off the warning light assembly at the bottom of your windshield frame rail and removing all bulbs in the headlight assembly. 

Test each wire with a multimeter for continuity. Continue testing until you find the source of your error (the wrong circuit is being energized). Once the problem wire is located, use a heat gun to melt the solder and cut off the bad wire. 

Cut a piece of wire about 6″ long and solder it in its place. Don’t remove the wires to make splices. You’ll just have to splice another one later. Once you’ve made your splice, re-insert the bulbs into the headlight assembly and test it. If everything works, re-assemble your warning light assembly and call it a day.



Frequently Asked Questions

Q. What would cause brake lights not to work?

There are three possible causes for this problem:

  • Brake light bulbs that aren’t working.
  • The electrical switch for the brake lights is broken.
  • A brake light system circuit has blown in the vehicle.
  • Grounding problems

Fortunately, all of these issues are easily identifiable and remedied.

Q. What could cause the tail lights to remain on?

A damaged brake light switch, broken trailer light plug, malfunctioning brake light switch blocker, or a broken wiring harness are all possible explanations for taillights that stay on even after the automobile is shut off. There are a variety of explanations for this, but you may check to see if the problem is with the brake lights.


Brake Lights Wont Work When Headlights Are On


Q. Are brake lights and tail lights the same?

They’re not the same. Brake lights turn on as soon as the driver presses the brake pedal, whereas tail lights are activated when the parking brake is applied, or the headlights are turned on. You can also identify it by its color: On most cars, the taillights are a standard red, whereas the brake lights are brighter red.

Q. How much does it value to replace a brake light?

Fortunately, a brake light is relatively inexpensive compared to other automotive parts. The cost to replace the brake light bulb is always low. The cost of a bulb ranges from $5 to $10, and the charging method is $20, so the total cost will be around $30.

Q. How to check brake lights?

This is the procedure to follow if you need to inspect your brake lights:

To begin, turn the key in the ignition. The ignition must be turned on to provide brake lights for a thorough examination. Also, ensure that the car is not in the drive and open the car door. Next, locate a ground brush and place one end on the braking system. 

You can add pressure to the accelerator while monitoring the brake lights. Vehicle owners can now apply pressure to the brake pedal until it engages and locks in place. You can now get behind the wheel and inspect the brake lights.


Brake Lights Wont Work When Headlights Are On


Final Words

It’s a common problem in cars; the brake lights don’t work when headlights are switched on. If you are new to car driving, you might give several dollars in repairs. 

But if you study your car correctly, the problem becomes minute, and you can solve this problem by yourself. You can also take the help of experts if needed. But a prompt action will save you a couple of dollars and harassment. 

Thank you for reading the article, we hope we were able to help you solve this critical problem. You might also like to read: Brake Lights Only Work When Headlights Are On

Photo of author

Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

Leave a Comment