Why is the car brake light on?

[DelMicah]

Reasons for the car brake light being on: 1. Insufficient brake fluid; 2. Damaged brake switch; 3. Worn or aged brake pads. The brake light is generally installed at the rear of the vehicle, with a main color of red to enhance the penetration of the light source, making it easier for vehicles behind to detect the braking of the vehicle in front even under low visibility conditions, thereby preventing rear-end collisions. Car brake lights can be categorized by position into 3 types: 1. Rear brake lights; 2. Brake indicator lights on the dashboard; 3. High-mounted brake lights. Car brake lights can also be categorized by material into 2 types: 1. Gas car brake lights; 2. LED car brake lights.

[VonCali]

I just dealt with this situation a few days ago when repairing a car. The brake light coming on is most likely due to worn brake pads. Many vehicles nowadays come with wear sensors, which trigger when the pad thickness is insufficient. If you hear a metallic scraping noise when braking, that further confirms it. It could also be because the brake fluid reservoir level is too low. Pop the hood and check the translucent reservoir; if the fluid level is below the MIN line, top it up with some DOT4 brake fluid. Don't take it lightly—once, a client ignored it, and air got into the brake lines, nearly causing a rear-end collision. Get it checked as soon as possible; safety-related matters are nothing to be careless about.

[Barbosa]

I've encountered three common causes that are most worth checking. First, try restarting after turning off the engine—the electronic parking brake module might be malfunctioning and giving false alarms. Second, check if the brake pedal is stuck by the floor mat and hasn't returned to its position, which can keep the brake light on. Third, inspect the brake light switch, that small button behind the pedal linkage; if it's worn out or faulty, it can trigger false warnings. Once, my car's light came on after heavy rain, and it turned out the wiring in the spare tire well in the trunk was soaked. As a side note, a damaged or short-circuited brake pad sensor wire can also cause false alarms, so older cars need extra attention to wiring aging issues.

[DiBrody]

This needs to distinguish between the handbrake light and the entire vehicle brake warning light. If it's just the handbrake light with a circle and exclamation mark, it's most likely that the handbrake isn't fully released or there's poor sensor contact, which can easily be triggered when parking on a slope. If the red brake exclamation light comes on, you must pull over immediately! It's highly likely that there's an issue with the brake force distribution system, possibly due to a leaking single-side wheel cylinder or an abnormal ABS pump. Last winter, my colleague's car had this light on because the brake fluid contained water that froze. Northern car owners should remember to change their brake fluid every two years.