What are the four wires of the brake light switch?
1 Answers
Automobile brake light switches have four wires: one is a 12-volt power supply, the other two are brake signal wires to the ABS system ECU and the automatic transmission ECU, and the last one goes to the rear brake indicator light. In some high-end models, the ABS and automatic transmission share one wire, with an additional brake signal wire to the electronically controlled suspension. Below is additional information: 1. Principle: To understand the principle of a four-wire brake light switch, first, you need to know the principle of a two-wire brake light switch. A two-wire brake switch is a break-make type—it connects when the brake is pressed and disconnects when the brake is not pressed. The positive terminal directly supplies power to the brake light. A four-wire switch consists of two brake switches: one normally open and one normally closed. When the brake is pressed, the normally open switch connects, and the normally closed switch disconnects. 2. Testing the brake light switch: To check the condition of a four-wire brake light switch, a multimeter is required. Set the multimeter to the diode measurement mode. Use the red and black probes to measure. If any two pins conduct, they are the normally closed contacts. The remaining two are the normally open contacts.
