The brake warning switch from the Datsun 240Z is a simple design. It detects a difference in hydraulic pressure between the front and rear brake system and alerts the driver via a warning light on the speedometer gauge. The unit receives the front and rear brake lines from the brake master cylinder. It splits the front between left and right while the rear is sent via one line and is split between left and right at the rear proportioning valve. When a loss of hydraulic pressure is detected at any point beyond the unit’s exit ports of around 13 to …