The brake light switch is the electrical switch that is responsible for activating the brake lights. When the pedal is pressed, the brake light switch makes contact, and the the brake lights are illuminated. While the exact designs of brake switches can vary, they all serve the same purpose of activating the brake lights when the pedal is pressed. As the brake lights are what alerts the drivers behind you that you are slowing the vehicle, the brake lights and the switch that activates them become inherently important to vehicle safety. When the brake light switch does fail, usually the vehicle will produce a few symptoms that can alert the driver that a problem has occurred.

Brake lights stay on

One of the symptoms commonly associated with a bad brake light switch are brake lights that stay on at all times. If the brake light switch shorts internally it may cause the brake lights to stay illuminated, even when the pedal is not being pressed. This will cause the brake lights to burn out sooner than they should, as well as create a parasitic drain on the battery.

Brake lights do not function

The other symptom commonly associated with a bad brake light switch are brake lights that do not function at all. If the switch fails, it will not be able to activate the lights when the pedal is pressed, and as a result the lights will not function.

Because brake lights are what alert the vehicle’s behind you that you are slowing, if there is any problem with the switch that activates them, the overall safety of the vehicle is compromised. For this reason, if you suspect that your vehicle’s brake light switch may be bad or failing, have the brake lights inspected by a professional technician, such as one from YourMechanic, to determine if you need a brake light switch replacement.

This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Brake Light Switch and was authored by Ed Ruelas.


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