Check the fuses for your brakes.
the turn signal switch is probably bad
check fuses then check all the bulbs, then check the turn signal switch the brake lights work through it
Since most brake/turn use the same filament in the bulb(1157) then if the turn signal switch is bad or offset then it will effect the brake lights.
blubs blown? Check the turn signal switch.
It depends on the exact problem. If it's that both brake lights in the back do not work and the middle one works, it could be your turn signal switch.
it is the turn signal stalk. here is a good writup for repair. http://tss.likeabigdog.com/
I'm guessing you're talking about your turn signal light. From what you wrote I think I'd have to say it sounds like a bad turn signal switch. The brake lights run through the turn signal switch on mostly all vehicles.
Check and make sure you have the correct bulb. The turn signal/brake light is a dual element bulb and if you have a single element it does not work properly.
Check turn signal switch. Pull back lighty on turn signal lever and brake lights will come on. Replace switch inside steering column. The green and yellow wires you see at the bulbs are the ones that control the brake lights and turn signals.
It could be a blown fuse. Tail lights and brake/turn are on separate fuses. Apparently there is not a ground problem since brake/turn works OK.
One of two things. Either the brake light switch behind the brake pedal. Or try wiggling or rotating your turn signal stalk in a circle motion. If the brake lights work when the turn signal stalk is wiggled then you need to replace the turn signal stalk.
It's the turn signal switch which is the culprit.