In some vehicles, a consistently lit turn signal indicator dash light acts as an error message. What the light could be saying is that either the bulb is burnt out and needs replacing, or there is an error with the related fuse.
The turn signal flasher relay is defective, replace it.
Defective turn signal switch.
Get a new blinker unit.
the turn signal switch in the steering column
If you turn on your 1999 mustang v6 car and the right signal light stays on and doesn't blink and you switch the car off and then the left signal light stays on without blinking, then you need to see a mechanic.
One of the bulbs is burnt out.
A turn signal that doesn't shut off when you straighten your wheel means the trigger inside is probably broken. To repair it you will probably need to replace your turn signal switch
I've seen some turn signal dash indicators that stay on without flashing just when a bulb is burnt out. If the signal itself is flashing, and especially if the turn signal arm doesn't automatically retract when you turn, there may be a broken spring in the canceling cam inside the steering column.
Sounds like you simply have A burned out bulb, Turn the signal on and look at all the lights to see if any are burned out. Could be A marker light if its in the turn signal circuit.
You have a burned out bulb on the right side. Even a the side marker bulb will affect the turn signal
Flasher is under the dash, drivers side, follow the clicking sound the signal makes when turned on. That sound comes from the flasher. If signal is staying on it could be you have a bulb or two out. Check your signal lights before replacing the flasher.
First thing is to check for a burnt out bulb in either the front or rear turn signal for the side that stays lit. Second, if the bulbs are fine then check for a bad turn signal fuse/cannister. Hope this helps.