Having a non-functioning brake light is not only unsafe, it is also a violation for which you can be issued a citation for. Brake lights give notice to the vehicle behind you that you’re slowing down, and hence they should slow down lest they rear-end your car. Because of the danger involved, the authorities have seen it fit to make functional brake lights mandatory.
But over and above that, to a car freak like myself, a non-functioning brake light is a mortal sin. This is because it just makes a car look broken and run-down. And we all want to be in nice presentable cars even if they are old, don't we?
Thus, if you find that one, two, or all three of your brake lights have stopped working, here are a few run-of-the-mill brake light problems and their remedies:
1) The bulb is out
Sometimes, a failed brake light is as simple as replacing a broken bulb. This is probably the most common reason for a brake light failure. The way to check this is by going behind the taillight assembly, usually inside the trunk or in the cargo bay. The assembly can be taken out and the bulb removed from the socket to check if it's in good condition. If it's burnt out, it doesn't take too much effort to go to an auto-supply store to get a replacement and reverse the process above.
2) A burnt fuse
If just one brake light is out and all three bulbs are good, it's most likely a burnt or blown fuse. The location of your fuse panel is usually in your owner's manual. Once you've found the fuse panel there's a description under the lid that describes each fuse. Find the one appropriate to the brake light you're looking for.
There's normally a fuse puller right under the fuse panel lid, or use a pair of needle nose pliers and pull out the fuse. Once you've pulled out the fuse you're looking for, check to see if the fuse element is still whole. You can tell if it's blown or burnt just by looking at it. If the element is broken, get a new one in the same amperage from your local auto store. Stick in the new fuse and check if your brake light is now working.
3) Malfunctioning brake light switch
This one is fairly easy to diagnose. If all of your brake lights are out—meaning both taillights and the third brake light—most likely it's your brake light switch that's malfunctioning. The bad news is that this problem isn't an easy fix for a newbie.
I'd like to tell you that you can do this yourself, but if you're new to cars you're better off going to a mechanic to have this replaced. Primarily because the brake light switch isn't found in the same place for all cars. For you to find this switch you'll need the car's service manual which will tell you where it is. However, most of the time this manual can only be found at the dealer. So bite the bullet, break out the wallet, and go to a qualified auto electrician to have this part replaced.