Reasons Why the Brake Lights of the New Mondeo Stay On and Cannot Be Turned Off
3 Answers
Brake fluid level is too low or there is a brake fluid leak, brake pad wear alarm. Brake fluid level is too low: First, ensure that the handbrake is fully released, then open the engine hood. The brake fluid reservoir is usually located on the right side of the engine compartment, marked with MAX (maximum level) and MIN (minimum level). If the level is below MIN, it is necessary to check and add brake fluid at a repair shop as soon as possible. Brake pad wear alarm: When the brake pads wear to the limit, it will trigger the brake system alarm. The brake pad alarm system involves inserting an alarm wire into the brake pad. If the brake pad wears excessively, it will rub against the sensor wire, causing the sensor wire to break or come into contact with the brake disc, leading to a change in resistance. This results in a change in current, ultimately triggering the alarm.
I've encountered this issue quite often where the brake lights refuse to turn off, and it usually requires checking a few key areas. The most likely culprit is a faulty brake light switch, which is hidden behind the brake pedal—when you press the pedal, a small switch gets depressed and should release to turn off the light when you let go. However, over time, this switch can get stuck or fail entirely, causing the light to stay on. Next, check the fluid level sensor in the brake fluid reservoir; some vehicles use it to control the light, and if the level is too low, it can trigger a false illumination. Wiring issues shouldn’t be overlooked either—if the brake light wiring is frayed and grounding out, it’s essentially supplying constant power to the bulb. Sometimes, aftermarket trunk liners can pinch the wiring, or incorrectly installed aftermarket brake light accessories may cause abnormal prolonged illumination. Get it checked ASAP—not only does this drain the battery, but trailing drivers might think you're constantly braking, which is both unsafe and wasteful on the battery.
From what you've said, the issue with the brake lights not turning off needs serious attention. The core problem is most likely the brake light switch, which is located above the brake pedal in the driver's seat, designed with a metal rod or plastic arm. If it gets pressed down and doesn't spring back, it needs replacement. Another less common issue is the brake vacuum booster; when it leaks, it can affect the brake pedal's return, indirectly jamming the switch. Also, check the wiring connectors on the rear panel, especially in older cars, as aging wiring harnesses can easily fray and short-circuit, keeping the lights on. Once saw a case where heavy items in the trunk crushed the wiring harness, causing a short circuit. Delaying repairs can drain the battery, making it hard to start the car, and bulbs may burn out. If this happens, address it immediately.
