Left turn signal lights up but does not blink

[82GMCSierra]

My left turn signal does not work. Right turn ok, and hazard lights ok and all bulbs flash accordingly.

When I apply left turn signal, the indicator inside lights up, but does not blink.

Where should I start looking first?

Thanks,
Neil

 

[82GMCSierra]

Answered own question. It had thrown alternator belt and evidently didn't have enough juice to make it blink.

Replaced belt and it's working now.

Odd that all the other stuff worked except left turn.