Brake Light Repair

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.

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.


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)