The 1999 Mercury Sable license plate light and the right side brake light are on the same fuse. If the fuse was bad neither brake light would work. The problem probably is burnt out lightbulbs.
Put this question into google, and you will find many reasons and remedies to this problem. Ei...brake light switch, brake light bulbs, including the upper brake light bulbs.
There are brake lights in 2 places - the taillight housings and the center/high-mount.See "Related Questions" below for more about removing the covers and accessing the bulbs for both locations.
check all your ground wires
Change brake light bulbs Just remove the rear license plate. You can change the backup lights and brake light easily.
AnswerThe brake light switch will probably need replacing. This is normally located on the arm of the brake pedal. Looks like a push button switchSee "Related Questions" below for more
There are a couple of bulbs in the taillight: turn, brake & backup.See "Related Questions" below for a Taurus/Sable lightbulb-round-up...
check the switch at the break peddle
You have to diagnose the system to determine the cause. Check the fuses, the bulbs, the flasher relay then the switch.
You could have a bad brake light switch, bad bulbs, or a short in the wiring. Try changing the bulbs first. My Camry was doing the same thing. I put in new bulbs and no more problem.
Check bulbs Check Fuse Check stop light switch
Other than at the back of the car... (?) If the question is about how to change brake light bulbs, See "Related Questions" below If the question is about the brake light switch, that's on the brake pedal - just a couple of wires going to it and rather easily replaced.
Are all the bulbs burned out maybe? Possible bad fusable link. Check fuse box with key on to make sure you're getting power there to all the fuses. If no, replace fusable link.