Brake light failure is caused by a blown fuse, burned out light bulbs, or broken brake light wiring switches. Periodic brake light testing prevents unknown brake light failure.
All three brake lights are connected to the same power distribution center. If all three bulbs don't light up, this usually signifies an electrical system problem. A burned out bulb often consists of a blackened or cracked filament, or a broken bulb. Burned out bulbs cannot be repaired, so they must be replaced.
The brake light wiring switch is next to the brake pedal and has two wires. The brake lights light up when the power flowing into and out of the switch both work. Both the incoming and outgoing power must work or the switch wires need replacing.