Depends on the vehicle. Resubmit your question with vehicle make, model and year.
REPLACE THE BULB
probably your blinker switch (multi-accessory switch). The high mount brake light is wired directly from the switch on the pedal but the rear two lights are wired through the pedal switch and then through the the blinker switch on the steering column. Almost all of those blinker switches go bad.
Hmmm, kind of unusual because the same bulb filament serves BOTH the blinker and the brake function. It could be a short in the wire from the brake switch leading back to that particular bulb and if the left brake light work okay it would have to be somewhere AFTER the wires leading to the rear lights branch off from one another. Are you CERTAIN that the right rear signal blinker DOES work?
Nonfunctional Brake LightsOne possible cause of this issue is that the brake light switch is not adjusted properly, or the switch could be defective.
Black=Ground Purple=blinker Blue=light+brake
There might be a break in the wiring.
try changing the build i think it has a double fillement build that works with the brake light and blincker
no, just one solid one, also used as the blinker.
Your rt side brake light is burned out.
Bad earth connection at light cluster?
There is no such thing as blinker fluid, a blinker is a turn signal light. They do not require any fluid. Brake fluid goes in at the firewall in front of the driver there usually is a plastic top with a round metal thing behind it.
How about a malfunctioning brake light switch