Brake lights are an important part of the car safety system. Their function is to remind the rear vehicles to slow down or stop to avoid rear-end collisions. However, sometimes we find that the brake lights are always on, which may be caused by a variety of reasons.

1. Lack of brake fluid
Brake fluid plays a vital role in the car's braking system. When the driver steps on the brake pedal, the force from the pedal is transferred from the piston of the master brake cylinder through the brake fluid to the brake cylinders located at the wheels, so that the brake pads contact the wheels to stop the vehicle from moving forward. If the brake fluid is missing, not only will the brake lights be always on, but also there will be a significant lack of braking force, and even a loss of braking force in severe cases. In this case, the driver needs to replenish the brake fluid in time to ensure the normal operation of the braking system.

2. Damaged brake switch
The brake switch is an important component that connects the brake pedal and the automotive brake light. When the driver steps on the brake pedal, the brake switch triggers the brake light to light up. However, if the brake switch is damaged, or the brake pedal and the brake sensor switch are not in good contact, the brake light will stay on. In this case, the driver needs to disassemble the brake pedal and check whether the brake switch is damaged or whether the contact between the brake pedal and the brake sensor switch is good. If a problem is found, the brake switch needs to be replaced in time or the part with poor contact needs to be repaired.

3. Wear and aging of brake pads
The brake pad is a key component in the automobile braking system. It directly contacts the wheel, generates friction, and slows down or stops the vehicle. However, as the use time increases, the brake pad will gradually wear and its thickness will gradually decrease. When the brake pad is worn to a certain extent, it may cause the brake light to stay on. In addition, severely worn brake pads may crack during driving, causing danger. Therefore, the driver needs to check the thickness of the brake pad regularly. If the thickness of the brake pad is found to be lower than the specified value (generally 0.8cm), it is necessary to replace the new brake pad in time to ensure driving safety.

4. The handbrake is not released
In addition to the above-mentioned fault factors, it may be that the owner forgets to release the handbrake and the brake indicator light stays on. The handbrake is an auxiliary braking system of the car, usually used when parking to prevent the vehicle from sliding on a slope. However, if the owner forgets to release the handbrake during driving, the brake light will stay on. In this case, the driver needs to check whether the handbrake has been released. If the handbrake is not released, the handbrake needs to be released in time to avoid the brake light being on all the time.

5. Damage to the brake light bulb
The brake light bulb is an important part of the brake light system. It is responsible for emitting light to remind the rear vehicle to slow down or stop. However, as the use time increases, the brake light bulb may be damaged, causing the brake light to be on all the time. In this case, the driver needs to check whether the brake light bulb is damaged. If the bulb is found to be damaged, it is necessary to replace it with a new bulb in time to ensure the normal operation of the brake light.

6. Brake light circuit failure
The brake light needs to be turned on through the circuit system. If the brake light circuit fails, the brake light may be on all the time. In this case, the driver needs to check whether the brake light circuit is unobstructed. If a circuit failure is found, it needs to be repaired in time to ensure the normal operation of the brake light.

7. Brake light relay failure
The brake light relay is an important component that connects the brake light and the power supply. If the brake light relay fails, the brake light may be on all the time. In this case, the driver needs to check whether the brake light relay is working properly. If a relay failure is found, a new relay needs to be replaced in time to ensure the normal operation of the brake light.

There may be many reasons why the brake lights stay on. Drivers need to check and repair them in time according to the specific situation to ensure the normal operation of the brake lights and ensure driving safety. At the same time, regular inspection and maintenance of the car's braking system is also an effective way to prevent the brake lights from staying on.