Ok, yes I bought a cheap set on eBay. They are ~ 1 year old. my drivers side light blinks when I turn it on but doesn't stay on. Is that the bulb or the ballast? I'm guessing the Ballast since the bulb looks like it is trying with the blink but I don't know enought about this technology to know what this means.

 

Swap ballasts side-to-side. If the problem follows the ballast-it's the ballast.