Same issue happened to me but only right turn signal flashes fast, checked the bulb which isn't blinking but its not blown too. Removed the flasher relay and checked with test light the relay clicks faster. Flasher relay was closer to the center console next to the steering column shaft fixed on a metal L mount bit deep inside and not with the usual fuse box. Had to remove the panel under the steering for easy access (Nissan Bluebird SU14)
