91 cutlass cieara (turn signal problem)

I'm having a problem with my left turn signal, when i put my left blinker on the signal light stays on and doesn't blink. the right siglnal light blinks just fine. i dont know what the problem is. I ckecked all the lights and there all working. help..

Remove the rear tailight, leaving the lights exposed. Turn on the turn signal and make sure they are lit! If in doubt, remove other side and see what blinks on the right side.

Flasher is not an issue here, if the right side works.