It depends on the car. Some cars require that you turn on the turn signals to make the 4-way flasher work. If that's the case with your vehicle, make sure the emergency flashers aren't on. Otherwise, it's probably a problem with the turn signal switch.
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.
Signal lights staying on withot flashing indicates either front or rear signal bulb not working on the Audi
You either have a bulb burnt out or the turn signal flasher is bad.
Look for either a blown fuse or replace flasher unit for the signal lights (it is separate from the hazard lights flasher unit).
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.
signal lights not working.
If the lights blink fast on either side of the car then this means you either have non-factory bulbs in the car or you need to replace your blinkers because one of your lights is out.
There are separate fuses for trailer signal lights in main fuse panel
1989 silverado left turn signal set applying brakes causes the left turn signal to dim and the two right rear tail light bulbs to alternate brightly? Further problem occurs to same truck - in Park and brakes not applied -- if head lights are on turn signal flash slows right down almost to a stop and becomes very dim
A mis-wiring or short circuit somewhere between the controls, fusebox and lights.
you need to change the flasher can for the signal lights