My left turn signal works only when it wants to. The whole assembly was just replaced by a reputable shop in town. Could it be a bad bulb? and how do I access it to check the hookup?

 

well, if it works sometimes, then your bulb should be okay, probably a connection, maybe not tightened all the way, or some water could have gotten in yoru taillight assembly.

 

It can definitely be the bulb...my turn signals seemed possessed and it turned out to be a intermittent filament inside one of the bulbs...while driving my turn signals would work semi-normally, but never when sitting still. They're cheap, but you can always swap them with the right side one at a time if you just want to test it out first.

 

this is funny, I have the same problem on my left blinker. Here is what happened. GM designed a pretty crappy sealing rear tailight which condensates and accelerates corrosion on the turn signal receptacles in the rear. This can cause the light to stay in a constant non-blinking state which if left long enough will burn the housing on the front blinker due to the heat buildup. I need to replace the housing on the front now, but I'm getting one from a salvage yard because GM tries to sell a turn signal wiring harness vs just a receptacle. I may have to replace the one in the rear as well. It's just a matter of cut-n-splic and replace with another receptacle. You may be able to clean yours enough with emery cloth.

 

I just realized we never answered the second part of your question....

To access it, for the rear just pull the carpet in the back away and undo the thumbscrews. The front requires removing the lower access panel...half dozen or so socket head screws. Both are pretty easy to get to.