What year/make is the vehicle? Something is suspect here. If the blinkers in the rear won't work, then the ones up front won't work either because there won't be enough load on the system to cause the flasher to work. What I think, is that you probably have one of your 1157 bulbs put in wrong and it is screwing up the system in the back. In fact, if you hit the brakes, I bet the front driving lights are illuminating. Get somebody to watch.
First, check all fuses. Then see if you are getting power to the bulbs. Then the next possibility would be the turn signal switch.
Answerpull the bulbs on the left and make sure they are not in with the tits in the wrong position. That is lower teet in the upper slot of the socket.
Check the switch on the brake pedal
brake light switch would be most common cause
The BOO (Brake On/Off) Switch may need to be replaced. If it is bad, it would cause the brake lights to NOT illuminate when the brake pedal is applied.
BAD BRAKE LIGHT SWITCH AT TOP OF BRAKE PEDAL
Possible ground issue at the taillights.
Blown fuse or defective brake light switch.
Most likely a fuse.
The most likely cause is a bad brake light switch (if none of the brake lights illuminate) but if its only one of the brake lights, try changing the bulb. Even if they still work as running or turn lights because they have a double filament and may still work partially, but not as brake lights.
The most probable cause is that the brake light switch is out of adjustment.
Nonfunctional Brake LightsOne possible cause of this issue is that the brake light switch is not adjusted properly, or the switch could be defective.
It could be a couple of things. On some vehicles, if one of the bulbs burn out in the taillight or turn signal circuit, both will stop working, but only on that side of the car. Some cars also have the brake lights wired through the hazard flasher, which if malfunctioning, can cause problems for both circuits, on both sides of the car.
More than likely it is the brake light switch that is attached to the brake pedal.
Check your brake light switch at hte brake pedal.
every vehicle must have brake lights to indicate that the vehicle is stopping. with no brake lights the vehicle can cause a rear end collision.
brake switch located on the top of the brake pedal
You probably need to replace your brake light switch. It's near the top of the brake assembly, beyond a trim panel. The fact that all three brake lights don't work rules out problems in the multifunction switch (the cause of similar problems affecting only the two rear lights.)
This is usually cause by a stuck brake light switch on the brake pedal. Replace it.
Could be a bad wiring harness, disruption of the circuit somewhere between the brake pedal and the brake lights, a bad switch which fails to actuate the brake lights. See sources and related links below for bulb information.
Have you checked to see if the fuses are still good. It might also be that you just need to put new bulbs in. Worst case senerio is you have an electrical problem. Have you checked the earth contacts and cables? Poor earths cause strange effects.
bad switch on brake pedal? do you have brake lights?
The most common cause for brake lights to be out on a 2001 Mustang GT is a blown bulb. There are some instances where there is faulty wiring.
A loose or corroded ground wire will cause the fuse to blow. Check the ground wires on your brake lights.