If your brake lights are not working, do not freak out. The solution is most likely relatively simple. Here are the two most common reasons why your brake lights are not working, as well as steps to fix each of these issues.
#1 Corroded Socket
One of the most common reasons that your brake lights may have gone out is that the socket you screw the light bulb into has become corroded. On many vehicles, it's be easy for water to get into the sockets and corrode them over time. Luckily, you should be able to fix this issue.
In order to get to where your brake lights are located, you are going to need to use a screwdriver to take off the protective lens that covers them. Place the screws somewhere safe as you'll need them to reattach the protective lens.
Get Rid Of The Corrosion
Your first and easiest option is to get rid of the corrosion inside of the damaged socket. All you need to do is take a rag and soak it in some white vinegar. Then take the rag and put it inside of the socket and let it sit and soak the corrosion for about an hour. This should break down the corrosion inside of the socket. When you pull out the rag, wipe away the corrosion. If any rust is still in place, scrub it away with a small metal brush.
Install A New Socket
Your second option is to take out the damaged socket, especially if the rust is advanced and has created holes within the socket, and put in a new one. You can purchase a new socket at your auto parts store, remove the old one and put the new one in place, or you can ask a mechanic at an auto repair shop to do this quick job.
#2 Burned Out Light Bulb
The other reason why your brake lights may not be working is simply because the light bulb has burned out. Like with step one, you will need to remove the protective lens that is over your brake lights to get to the light bulb.
When you do so, check the light bulb and see if the filaments, or wires, inside of the bulb look like they have become burned. If you can't tell from looking at the light bulb, unscrew it from its socket and gently shake the light bulb. If the bulb is burned out, you will hear a small rattling sound if the light bulb is burned out, and you'll hear nothing if the light bulb is fine.
If it is burned out, take the light bulb to your local auto parts store, and they should be able to help you secure a replacement. Screw the new light bulb in place, test out your brake lights with the assistance of a friend, and then screw the protective lens back in place.