If you're talking about the stop lights, the red ones on the back, that happens because your stoplight switch is stuck. Not usually a difficult thing to fix, and if you're somewhat handy you can save quite a few bucks by replacing it yourself. If it's a Ford, it may be a little to a lot more complicated.
Please fix it soon, because drivers behind you won't know when you brake.
The stoplight switch is usually located under the dashboard, above and behind the brake pedal. When you step on the brakes, the switch is activated, turning the lights on. When you release the brake pedal, it's supposed to disconnect, turning the stop lights off.
To troubleshoot using the process of elimination, crawl under the dash, locate the stoplight switch and disconnect ONE of the wires leading to it. BE CAREFUL - don't touch the wire, the terminal nor the pliers you may be using to ANYTHING metallic. If you happen to remove the "hot" wire, the one that is hot all the time (the wire that provides power from the battery to the switch, as opposed to the wire that goes from the switch to the stop lights, which should only be hot when the brake lights are on), it will cause a dangerous arc if it touches metal.
You can avoid that problem by disconnecting the battery before removing the wire. Caution: Turn everything electronic, e.g. stereo, etc. off before disconnecting the battery.
After disconnecting the wire from the stoplight switch, re-connect the battery momentarily. If the stop lights don't come on, the problem is in the switch.
The people at an auto parts place usually are very helpful in explaining how to replace things.
on my 03 Elantra, there is a plastic "spacer" that the tip of the switch touches to turn off the switch(brake lights) off. Plastic spacer crumbled and replaced it with a nut and bolt that had the same thickness. Problem solved.
my brake light stay on but emergency brake is unhooked
The brake light switch is broken or out of adjustment.
Probably a brake light switch.
Bent brake light switch bracket above the brake pedal.
STICKING BRAKE LIGHT SWITCH AT THE TOP OF THE BRAKE BEDAL
The parking brake light stay lit on the 1999 Mitsubishi Montero sport the parking brake is working and you have not put the light off.
check the brake light switch
Have you checked your brake fluid?
It is important to know what the meanings of the emergency lights on a ca. A brake light would stay on in a car because the brake system needed to be fixed, and the light needed to be reset.
The brake indicator light is for the EMERGENCY break, release this break.
Brake lights? Check brake light switch for adjustment or replacement
Defective or out of adjustment brake light switch.
The brake light on most vehicles is not only an indicator that the parking brake is on, but that there is a problem with the system.
Stuck brake light switch, or a short to power somewhere in the brake light circuit.
Brake light switch out of adjustment or defective
check the brake light switch it may have come loose
The brake light switch is either defective or out of adjustment if applicable.
You could be low on brake fluid.
Brake light switch either out of adjustment or defective Should be located at upper end of brake pedal under dash
The brake light switch is bad. It's under the dash, and is switched by the movement of the brake pedal.
Is the brake fluid level LOW in the brake master cylinder in the engine compartment ?
Check the brake fluid level in your brake master cylinder in the engine compartment ( the brake light also comes on if the parking / emergency brake is applied )
Possibly a defective brake light swith stuck closed.
Brake light on 1994 Honda civic staying on.