Categories Braking System

What Are the Malfunctions of the Brake Light Switch?


The brake light switch (or brake switch) is a car part that everyone can replace if they are a little bit handy, but be careful; in some cases, this vulgar switch can cause you to immobilize the vehicle! We detail its operation in this article.

Brake light switch: constitution

It is because it opens or closes an electric circuit that this organ is called a contactor.

When the driver brakes and presses the brake pedal, he activates a push button that establishes a contact between two electrical channels to supply the brake light circuit.

When he releases the pedal, the push button is brought by a spring to the rest position and cuts the brake light circuit.

Location of the brake switch

It is placed just behind the brake pedal, which presses directly on its push button.

This position usually allows easy and fast replacement: you have to disconnect its electrical connector, unclip it from its support and do the opposite operation for its installation.

Malfunctions with the brake light switch

What Your Brake Fluid Indicator Is Telling You

On old-generation vehicles

Two possibilities of failure of the stop light switch can occur:

The most common, the switch does not close the electrical circuit during braking. The brake lights are no longer powered and do not light up; in this case, it is necessary to change the brake light switch as soon as possible for obvious safety reasons.

More rarely, the switch closes the circuit permanently, creating a nuisance for other users, especially at night.

On recent vehicles

The brake light switch is a sensor integrated into the vehicle’s electronic management system: it sends the information about the pedal being pressed to the relevant ECUs for:

control of the brake lights and activation of the emergency lights;

the engine management for the injection cut-off, for example;

and the robotized gearbox ECU for downshifting gears.

As a result, not only does the malfunction cause the lights not to come on with an error message, but it can also make it impossible to start certain vehicles, for example, those equipped with the no-brake-pedal start system.

Prices and supply of a brake switch

Depending on its design (metal or plastic), its price will rarely exceed $30 (from $4 to $30).

With the characteristics of your vehicle (registration certificate or the vehicle registration number), the easiest way is to go to the car dealer or an automotive supplier.

The use of commercial websites is of little financial interest here, as the shipping cost of the part added to its price will be more or less the same as the price of previous suppliers.

For instance, your lights don’t work anymore, and you want to check that your brake light switch is at fault. You have to disconnect the connector and connect its two ways with an electric wire (shunt); if the brake lights light up, your contactor is defective.

Hope you have enjoyed reading this article. That’s it for the malfunctions of the brake light switch. 

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