More fun with wiring

[85k10383]

My passenger side turn signal/marker light has decided to not work. I have installed an el cheapo replacement (made in China, sold at Advance) and it is also not working. Before I rip out my few remaining hairs and begin disassembling the wiring from the socket back to the dash, what might I have overlooked?
PS Is the replacement socket that LMC sells really likely to be any better than the POS I got at Advance?

 

[f1shman]

If neither the marker or turn signal work, check the ground.

The three wires at the socket will be blue, black and brown. Black should be your ground. Blue will be the turn signal feed from the switch in the cab and Brown should be the feed for the marker light circuit.

 

[85k10383]

I didn't even consider the ground, and that is probably the issue. As every bolt on the truck (with the exception of the header bolts LOL) comes loose every two weeks, its probably that. Thanks meng!