A master cylinder >hydraulic brake light switch is a crucial component in a vehicle's braking system. It is typically located between the master cylinder and the brake lights. This switch ensures the brake lights automatically turn on when the driver presses the brake pedal, enhancing safety by alerting other road users to a deceleration. The hydraulic operation of the switch uses brake fluid pressure to activate the electrical connection. This component is vital for ensuring quick and reliable signaling to trailing traffic.