Slight story time: 86 B2K sat for 25 years, I got it running good on a new weber.
So as the title says, intermittently I have no lights in my interior, I haven't had the truck for a terribly long time but I've been putting it together piece by piece, currently I have no radio in the vehicle. The Blower motor doesn't blow, ALL dash lights are intermittently working, I often have no cluster lights, no aircon lights, I can't adjust the heat or vents, I have a front valance (the front wing looking thing that goes over the windshield) all of these lights will go out at once, from the valance to the interior, so far all fuses look good and no smacking the dash or shaking of the car seems to make a difference they just come on when they feel like it. If someone has a good place to start I would love to hear it as I would really like some heat before this winter starts!

 

I would start by testing the headlight switch part of the combination switch and by testing the electrical part of the ignition switch. I've had similar symptoms, and have replaced both on my 1988 B2200 in the 27 years I've had it.