My left turn signal indicator is flashing normally on the dash, but no lights are flashing on the outside of the truck. When I turn on the hazards, same thing (right side works not the left). Several weeks prior I had noticed that the left side rear light was not flashing when a trailer was connected. (May not be related). I pulled the flasher relay and re-seated it with no change. Any ideas, I'm stumped.
Brad

 

Not very probable that both front and rear bulbs are bad, but it's something to check. Also check where tow connector was wired to left tail light. Might have broken a wire,,,,,Use a test light and see if the wires feeding the front and rear lights have 12 volts entering the fixture when the TS or hazards are activated.