Brake Light Repair

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. Visit - Fuse test

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.


Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-01-05)