1999 Ford Explorer Turn Marker

What exactly do you mean by everything ese works?
Do you have directionals indicating on the instument panel?
do you have front signals and no rear or vice versa or do you not have any directionals and no emergency flashers?

If you do not have any type of flasher you need to replace the flasher relay in the fuse panel.
If you have emergency flashers and your front signal work but rear do not the primary culprit may be the integrated circuit board that are attached to the composite tail lenses. You can buy the circuit board portion seperate from the tail lense and at a cheaper rate than buying the whole unit. Dealers try to sell the unit as a whole so you might want to pursue other avenues first..