Brake lights are an essential and mandatory element of the braking system. They are intended to warn other drivers that you are reducing your speed and, as a result, their malfunction can lead to accidents. If these lights remain on even when you do not apply pressure to the brake pedal, it is likely that the fuse has blown or the switch is damaged; check both to make sure the brake lights are working properly before you get back into driving.
Steps
Part 1 of 3: Check the Switch
Step 1. Disconnect the battery
You should always do this before performing any type of work on the car's electrical system; in this way, you are sure not to receive a shock or to damage some element. Use your hands or an Allen wrench to loosen the nut that secures the ground wire to the negative pole of the battery; then unplug the cable and fit it along the side of the battery itself.
- You can recognize the negative pole by the symbol "-" or by the word "NEG";
- It is not necessary to disconnect the positive lead.
Step 2. Put on your safety glasses
For this job you have to work under the dashboard, so it is essential to protect your eyes from falling debris. It is not necessary to use gloves, but you can choose to wear them to avoid pricking yourself with the cables.
- Wrap-around goggles offer the highest level of protection;
- Eyeglass-like models are sufficient for this job.
Step 3. Locate the switch connected to the brake pedal
This is a key located along the shaft of the pedal, higher than the surface on which you press your foot. When you activate the braking system, the rod presses on the button turning on the lights.
- If you are not sure what the location of this element is, consult your vehicle's maintenance manual.
- There is a small harness with multiple wires sticking out of the switch that is mounted directly behind the pedal.
Step 4. Unplug the wiring from the switch
This piece is held in place by a plastic housing on which there are release clips; it is sufficient to press the latter to disconnect the wiring and then pull it and separate it from the rest of the switch.
- Do not exert traction on the actual cables, as this could detach or tear them from the wiring block.
- Be careful not to break the plastic clips.
Step 5. Visually inspect the wiring
Look inside for burn marks and melted plastic. If the cables have overheated, the wiring may have been damaged causing the brake lights to come on constantly; any damage within this element could be responsible for the problem.
- Worn wiring must be replaced to ensure proper brake light operation.
- If you can't find it at an auto parts store, you need to order it from the dealer.
Step 6. Check the switch "return"
In practice, this element is nothing more than a long button that is pressed when you press the brake pedal. As you inspect, try to activate the pedal or press the switch itself, to verify that it returns to its rest position when you release the pressure. If nothing happens, it means that the switch is continuously "on".
- If it does not return to the starting position, the lights remain constantly on.
- Ask a friend to look at the lights behind the car to see if they turn on and off as you press and release the switch.
- If the action on the button causes no reaction in the brake lights, it is likely that the fuse has blown or the switch is broken.
Part 2 of 3: Install a New Switch
Step 1. Make sure the wiring is disconnected
Before disassembling the switch, you must be sure that the cable assembly has been disconnected. If you've already done this to inspect it, let it dangle while you deal with the switch; if not, detach it now by pressing the release clips and pulling the plastic housing backwards.
- Unless it needs to be replaced, you can reuse the wiring for the new switch.
- If you break the release clips, you can use electrical tape to hold the harness in place once assembled, so you don't have to buy a new one.
Step 2. Remove the switch from the brake pedal mechanism
The various car models have a different fixing system; if the way to proceed is not obvious or intuitive, consult the maintenance manual of the car.
- The switch is typically held in place with one or two bolts.
- Be careful not to lose the small parts, you will need them later to install the replacement.
Step 3. Insert the new switch
Once the old one is removed, place the replacement part in the same spot and use the hardware you unscrewed earlier to secure it in place.
If the old bolts are damaged, replace them as soon as you remove them
Step 4. Join the switch to the brake pedal mechanism and wiring
Insert the latter into the new element and fix all the connections you had to disconnect for the specific car model. At this point, the switch should be behind the brake pedal rod and connected to the vehicle.
- Connect the battery and start the engine.
- Ask a friend to stand behind the car to make sure the brake lights are working properly.
Part 3 of 3: Replace the Blown Fuse
Step 1. Locate the correct fuse box
Most cars have at least two boxes positioned in different areas of the body; one is usually located under the hood and the second in the cockpit on the driver's side. Consult your vehicle's maintenance manual to find out in which of the two the brake light fuses are located.
- In order to access the box, you must remove the cover or some pieces of the molding;
- If you don't have the maintenance manual, you can consult the automaker's website.
Step 2. Identify the fuse protecting the brake lights
Use the diagram in the manual and on the inside of the box lid to recognize it; when this element is burned, it can prevent the lights from turning on or leave them constantly on.
There may be more than one fuse serving the lights, in which case you need to check them all
Step 3. Remove it from its housing and inspect it for damage
Use a pair of fine-tipped or plastic pliers to take the fuse out of the box. If it has a glass body, look inside; if the metal inside the fuse is broken or blown, you need to change the part.
- If you can't see the inside of the fuse, check the ends for any burn marks or damage.
- Most fuses have a translucent cover that allows inspection; if this is also damaged and does not allow you to see inside, it means that the whole fuse is blown.
Step 4. Replace the damaged one with a new one that can withstand the same current rating (number of amps)
To know this value, just look at the table; Most automotive fuses are rated for current between 5 and 50A, but the exact figure is printed on top of the element itself. Insert the replacement in the housing from which you removed the burnt one; when finished, put the lid back on the box and all the pieces you had to disassemble to access it.
- Connect the battery and start the engine.
- Ask a friend to stand behind the vehicle to check that the brake lights are working properly.
