A brake switch is a safety device that is installed in a vehicle to prevent it from being started unless the brake pedal is depressed. This prevents the car from being started accidentally, for example, if the driver leaves the key in the ignition and goes to get out of the car without depressing the brake pedal.
If a brake switch is faulty, it can prevent the car from starting even when the brake pedal is depressed. This is because the switch may not be making good contact with the electrical circuit it needs to complete in order to allow current to flow to the starter motor. As a result, you may hear clicking sounds when you turn the key in the ignition, but the engine will not crank over and start.
If you suspect that your brake switch may be causing your car not to start, have it checked by a qualified mechanic as soon as possible.