Car Brake Lights Not Working

Brake Light Repair

Brake Light Issue  --  Brake Light Dim

Helpful Information

Brake lights are designed to warn the drivers behind that the car in front of them will be slowing down or stopping. A brake light system in most cases is a basic electrical system involving a simple positive and ground system controlled by a brake light switch activated by the car's driver. A system fuse is used to protect the brake light electrical circuit. The lighting system is activated by a switch located near the brake pedal arm. The brake light switch rests in the open position and closes (electrical contacts connected) when the brake pedal is depressed.

A major difference between American and Japanese-European auto manufacturers. The American car makers have incorporated the brake light circuit into the turn signal system, were as the Japanese and European auto makers design the brake and turn signal electrical systems separately. For these separate systems troubleshooting the same problem will be slightly different for these individual systems.

Best Practices

• A brake lens can melt and distort when the brake lights are kept on for an extended amount of time. This heated condition can also negatively affect the brake light bulb holder as well. Never allow the brake light to stay on overnight.
• Always replace brake light bulbs with manufacturers recommend replacement bulbs.
• Use correct replacement bulbs to ensure proper operation.

Step by step repair guide on how to fix brake lights. Additional problems covered in this section is how to repair a bulb that is dull or flickering. This article pertains to all non-LED lighting systems.

Difficulty Scale: 3 of 10

Tools and Supplies Needed

• Test light or voltmeter
• Sandpaper
• Safety eyewear and gloves
• Small screwdriver set

Begin with the vehicle on level ground, parking brake set while in park.

Brake Lights

Step 1 - All non-LED brake lighting systems utilize a 12 volt bulb which can fail. Visit -Brake light bulb replacement

Step 2 - A fuse is used to protect the brake light circuit from amperage overload. If the fuse has failed it will not allow the electrical current to continue to the brake lights.

Step 3 - A control switch is used to connect the brake light electrical circuit which is located near the brake pedal lever. Basic switches have just two wires, power in and power out, and then onto the turn signal switch (American cars only). Some cars are equipped with more than two wires integrated into the brake light switch, a wiring schematic is needed locate the proper brake light circuit wiring. Use a test light that is grounded, with the key in the "ON" position test for power at one side (wire) of the switch, then press the brake pedal while testing the opposite side (wire).  The test light should illuminate if the switch is good, if electrical power is good through the switch, go to the next step. If no power is detected the switch has failed and replacement is required. If the brake lights stay on continuously an adjustment of the switch is needed.

Step 4 - (American made cars only.) Both lower brake lights not working. Most American cars are designed to have the brake light circuit wiring integrated into the turn signal switch. The brake light bulb and the turn signal bulb are one and the same, the turn signal switch interrupts the brake light circuit and installs the blinker signal circuit when the turn signal switch is activated. If this switch fails it will not allow the brake light signal through to the brake light wiring. If brake light switch power is present at the turn signal switch but not at any outgoing wires the turn signal switch has failed and replacement is required. A wiring schematic can be helpful in testing the circuits.

Step 5 - Some cars are equipped with a body control module (BCM) or lighting control module (LCM), this on-board computer controls lighting signals which can malfunction not allowing the electrical current to continue to the brake light circuits.

Step 6 - Some Japanese cars such as Toyota, have a brake light control module which is usually located in the trunk or near the rear seat which can malfunction causing both lower or the center brake light to fail. Test the incoming power feed from the brake light switch. If incoming power is present without outgoing power replace the brake light control module.

Dim Brake Light Repair

Step 1 - Remove the bulb in question and confirm the correct brake light bulb has been installed. Next, turn the ignition key to the "ON" position and have a helper depress the brake pedal. With the bulb installed, touch a grounded test light to the outer bulb holder ring, (metal). If the bulb brightness changes, the bulb socket ground has high resistance and needs to be re-grounded to fix the problem.

Shorted Terminals

Step 2 - A brake light flickers because the power or ground is being obstructed momentarily. The most common cause for this condition is a loose fitting bulb socket. To check for this condition remove the brake light bulb in question, while a helper hold their foot on the brake pedal move the bulb around slightly in the socket. If the bulb flickers replace or repair the bulb socket as needed. If the brake light bulb socket tests okay wiggle the brake light fuse and wiring at the brake light bulb socket, brake light switch and turn signal switch (American cars). If the brake light bulb flickers repair the component or wiring as needed.