99 Blazer Turn signal

I've got a 99 Blazer that the left turn signal wont blink at night or in the garage.
Everything works fine during the day. I have installed extra grounds on body, battery and engine which took care of some other electrical problems but I'm scratching my head on this one. I searched the forum and the web and cant find a similar problem. Anyone have any ideas?

I forgot to mention, its only the left blinker that is affected.