Bulb could be out, blown fuse....
b/c your brak light is blown..and all the rest will work but that one.that or you have a fusa that is not working one of the 2
wiring.
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.
More than likely you have a burnt out bulb at the front signal light, rear signal light, or brake light on the right side.
If there is a light labeled right turn signal and it is red, you can not legally turn.
it could be a number of things 1. fuse 2. burnt our light 3. a short is my bet get it sheck out if its bothering you
If only the right rear brake/signal light is effected it is not the fuse. Inspect the right rear brake/signal bulb, socket and wiring.
change the light bulb,
The right side will have a burnt out/ missing light bulb.
You have a problem with your ground. A weak ground will always cause this type problem.
usually this is a bulb burned out on the left side
IF, the bulb doesnt light up at all than it is the turn signal balb but if the turn signal is flashing quickly, but still lights up like it should than it is quite possibly the turn signal phuse. And you need to check the phuse instead of thte bulb.