Check to see if the brake lamp and turn signal lamp are the same bulb. If so, its a bad bulb. See sources and related links below to lookup bulb information.
One of the bulbs is burnt out and not working.
signal lights not working.
Turn signal lights that double as parking (marker lights) when not blinking.
Turn on that fast blinking signal light and check to see if the front and rear signal lights are both working, chances are you have a burned out bulb. If both front and rear bulbs are flashing fast, replace the flasher relay.
It has been my experience that a rapid turn signal indicates there is a burnt-out signal light bulb (either front or rear) on the side of the rapid blinking signal. If the right signal is blinking rapidly, the problem is in the signal lights for the right side (front or rear) of the vehicle. Turn the rapid signal on and step out of the vehicle to find which bulb is not lighting.
change the flasher to a slower blinking brand. They are cheap and you can try a few brands
is the car on? do you have the signal on? is there a bulb? are there wires connected to the bulb? or just go to a mech and have him figure it out. simple.
Defective flasher relay.
either dimmer switch or blown fuse If you are saying that the tail brake lights are working but the third brake light is not....It may be a defective turn signal switch in the steering column.
Either hand signal or check and replace your fuses and turn signal bulbs.
When the signal lights are not working on a car, there are a couple of things that could be going on. One could be that the bulb needs to be replaced. The other possibility is that the signal relay needs to be replaced.
It's the turn signal indicator-located behind the hazard lights.You have to take it out and replace it.