5 Common Reasons Why Truck Brake Lights Not Working, How To Fix?

When it comes to driving, safety is paramount. One of the things that can help ensure road safety is to make sure that the brake lights and tail lights of your car are working properly. Brake lights light up whenever you step on your brakes to keep trailing motorists notified that they should slow down accordingly. In this article, you’ll find the most common issues of truck brake lights not working.

5 Common Reasons Why Truck Brake Lights Not Working?

When your brake lights don’t work, it is usually because of a blown fuse, a worn-out or broken brake light switch, or a burned-out light bulb. Let’s get an in-depth format of this problem.

1. Burnt Out Bulb:-

A burnt-out bulb is one of the brake light problems that crop up the most. Think of how much time you spend with your foot on the brake, and then consider that the bulb has to be illuminated during that entire period. Newer models have switched to LED lights that last much longer, but older vehicles still feature bulbs that need to be popped out and replaced. It’s cheap and easy to do, most of the time, with a basic set of tools.

2. Blown Fuse:-

If your lights don’t illuminate on either side and your brake light switch is good, then the next thing to check is the brake light fuse. Locate your vehicle’s fuse box, which is usually under the hood or on the kick panel inside the passenger compartment. Using the fuse diagram on the box’s cover or in the manual, find the fuse for the brake circuit and make sure it hasn’t been blown. If it has, replaces it with a fuse of the same resistance.

Car fuses

3. Electrical Ground:-

The electrical ground is one of the things you should also check if the truck brake lights not working. This could be a possible issue, especially when the brake light switch is functional. Check for the bad electrical ground which may be a result of corroded or damaged wires.

4. Bad Socket:-

If you have a single brake light out and the bulb is good, then the next step is to check the light socket itself. Brake light problems can include a socket whose connections are dirty or corroded or one whose wiring has become worn to the point where it’s only making an intermittent connection. Replacing a socket is simple.

5. Bad Brake Light Switch:-

When the brake pedal gets pushed, a switch is triggered to send a signal to the lights to turn on. Analog switches wear out over time, and they can get dirty, too, which interferes with their ability to make positive contact and transmit the right signal. Replacing the switch is not a big job. If all three brake lights are out at the same time, it’s unlikely that the trio of bulbs died simultaneously. In this case, it’s more likely a bad brake light switch.

Therefore, these are some common reasons behind the truck brake lights not working problem.

How To Fix The Bad Brake Lights?

It’s not always easy to notice when your brake lights are not working. Some modern vehicles make it easier for owners by producing a warning light on the dashboard to inform the driver of a bad brake light.

1. Check For Burnt Fuses:-

It’s always best to check your car fuses. Your vehicle could have up to three different fuses dedicated to each tail light. When either of these is damaged, you could either have just one, two, or all brake lights out. Take out each fuse and check if it’s burnt or broken in the middle. Turn your key ON and place the test light on each contact on the fuse. If you have a bad fuse, replacing it could solve the problem. However, fuses don’t just go bad on their own. It’s important that you check for corrosion, a wiring problem, or a connection issue at the tail light or brake light bulb. These could be the reason behind the burnt fuse.

2. Check The Trailer Connector:-

You’ll need to clean the connector and apply some dielectric grease to prevent further corrosion. Dielectric grease is a viscous substance that coats the car’s electrical connections to be waterproof and prevents future corrosion. This may, not only, fix your current brake light problems but could prevent further issues. Other times, you could have connected a trailer with an issue in its wiring which took out the lights without you noticing. You’ll need to check your brake lights and tail light bulbs to see if they are blown.

3. Test The Bulb Connection:-

You’ll need to test the terminals with a test light. Check for power and ground while someone steps on the brake pedal. To test for ground, connect the test light to the positive terminal of the battery and use the tip to test the terminals. Be careful not to touch more than one terminal at the same time as this could cause them to spark. If the test light lights up, then your ground is good. If your car has a third brake light, test it in a similar manner.

4. Test The Brake Light Switch:-

To test the brake light switch, take a jumper harness and connect it to the connector. You’ll have to first find out which wires go directly to the brake lights. Jump those wires by connecting them to the jumper harness. You can have someone check the brake lights as you do it.  If the lights work while you’re using the jumper harness, your switch is damaged and you’ll need to replace it with a new brake light switch.

5. Check The Bulb And Its Connection:-

Take your tail light bulbs out and check their connection. There could be rust that has accumulated over time. If that’s the case, you’ll need to clean it off. If there’s nothing wrong with the connection, check the bulb to see whether the filament is broken. Sometimes, it may look fine but still have an internal break. You can swap the bulb with a new one of the same type to confirm. If the new one works, you’ll definitely need to replace the old one.

Checking headlamps and lights | How a Car Works

6. Trace The Bulb Wiring:-

If you’re diagnosing that truck brake lights not working, you can trace the wires from where they connect to the bulb. Depending on the type of vehicle, they may go straight to the brake pedal or to a junction block. You may need to replace your tail light wiring harness or a damaged or corroded junction block.

Hence, these are some tricks you can try to solve the issue of the bad brake lights properly.


We hope the above-mentioned information about the truck brake lights not working will be helpful to all the readers. If anybody’s doubts persist feel free to comment in the comment section below. We’ll try to solve your doubts as soon as possible.

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