What are the four wires of the brake switch?

[DelJace]

The four wires of the brake light switch are: one is the 12-volt power supply, one is the brake signal wire to the ABS system ECU (ECU stands for Electronic Control Unit, also known as the vehicle's onboard computer), one is the brake signal wire to the automatic transmission ECU, and one goes to the rear brake indicator light. Below is some relevant information about the brake light: 1. Rear brake light: The rear brake light is controlled by the vehicle's lighting system. The brake switch does not directly control the rear brake light; instead, the brake switch signal first goes to the vehicle's lighting control system, which then controls the brake light. 2. Function: The brake light is highly bright and noticeable, primarily used to alert following vehicles that the car is slowing down or stopping. Incorrect use or malfunction of the brake light can easily lead to rear-end collision accidents.

[LaElle]

The four wires at the brake switch are actually clearly divided. One pair is specifically for the brake lights: one input wire receives power from the fuse, and the other output wire goes to illuminate the rear brake lights. The moment you press the brake pedal, these two paths connect, and the light immediately turns on to signal the vehicle behind. The other pair of wires is mainly for cruise control: one point is normally closed to keep the cruise system operational; the other end disconnects when the brake is pressed, instantly stopping the cruise function to prevent the car from moving uncontrollably. This design is quite clever, managing two functions with one action. If you notice the brake lights flickering or the cruise control stopping unexpectedly during normal driving, remember to check that the wires at the switch aren’t loose or corroded. Otherwise, small issues can lead to big hazards. Repairs are simple, but don’t disassemble it recklessly—watch some tutorial videos before attempting any work. If the wires are aged, replace them with original parts; safety is the top priority.

[MacKiara]

When it comes to those four wires on the brake switch, I've encountered them multiple times while tinkering with my car. A typical configuration consists of two circuits: one wire connects to the fuse box power supply providing 12V, corresponding to an output wire leading to the brake light bulb. As for the other two wires, they control cruise control cancellation—one is a normally closed contact receiving power input, while the other disconnects output upon braking to deactivate cruise control. Testing with a multimeter is straightforward: when not pressing the brake, the contacts should open or close as designed; otherwise, the switch is faulty. In practice, wire aging and contact corrosion are common issues, especially since the pedal's frequent movement causes rapid wear. During maintenance, it's advisable to clean connectors to prevent oxidation and opt for OEM-branded spare parts—don't cut corners with cheap alternatives, as incorrect wiring can lead to blown fuses at best or complete circuit failure at worst. DIY replacement of the switch costs just a few dozen bucks, but remember to disconnect power for safety during operation.

[ChloeLee]

The brake switch's four wires bear significant safety responsibilities—never underestimate them. Two connect to the brake light circuit, handling power input and light output; the other two cancel cruise control, interrupting signals to prevent hazards when braking. Wire shorts or switch jams can cause major issues: brake lights failing (leading to rear-end collisions) or cruise control failing to disengage (causing unintended acceleration). During routine inspections, check wire conditions, ensure plugs are secure and dry, and address any switch abnormalities immediately—no delays. Maintenance priorities: remove dust/rust, inspect for wire damage, and guarantee flawless function in critical moments. Lives depend on this—no room for negligence.

[Ortega]

Why does the brake switch have four wires? The principle is that it combines two switches into one. Two wires are mainly responsible for the brake light system, with normally open contacts that close when the brake is pressed, allowing current to flow and the bulb to light up. The other two wires manage the cruise control, with normally closed contacts that are connected when the brake is not pressed, and disconnect when the brake is pressed to terminate operation. This circuit design is efficient: the brake has higher priority, and its action synchronously shuts down unrelated functions. Each wire connects to different ports on the vehicle body, simply put, inputs and outputs correspond to their respective systems. Once understood, maintenance becomes easier, but avoid random modifications to prevent interference with other components. Understanding the basic mechanism makes daily use more reassuring.