A neighbor of mine is having problems with his turn signal flasher, it won't flash, the light in the dash stays on. He has to manually push the flasher lever up down, up down. I told him it was either the flasher unit located underneathe the drivers side dash near the fuse panel or a burnt bulb. It'* a 98 Buick LeSabre.
Had a similar situation happen on my 93 lesabre, their might even be a post in the forums. check if your hazards work. I checked mine and thats how i figured it was the flasher unit. Swapped the hazard(flash unit) to the turn indicator(flash unit) solved my problems. Hope it works.