No Lights at 4x4 Dash Selector

[mr98z71]

So I've had my truck parked for 6 months now (Welded in new body panels), took out my truck for the first time, no lights on the 4x4 selector switch, next day, started her up, 2wd was light up, couple days ago, no lights, couldn't shift in 4x4 and this time I really needed it. I am an electrician so measuring is nothing new to me, I just need a diagram or pointers and what and where to measure and what I should be getting, This will help me find out what's wrong with it.

Thanks!
Jo-eL