Trying to figure out why my dome light will not work, have replaced the headlamp switch for another issue. Looking for a wiring diagram or some insights. before anyone asks yes i put a new bulb in it.
Yep, pretty easy to pull one from your door frame and check that the switch is still good. Probably the most failure prone point in that circuit.
Just be careful that the wiring doesn't fall back into the door, and don't cross-thread the switch into the door jamb. If those threads get loose, then the light will never work consistently.

What year K5?
Does it light up when you turn the headlight knob counterclockwise? It should.
Have you checked the fuse? I know that it is tied in with something else, I forget what at the moment. I am just thinking that there may be more possible problems besides the one that you already found.
Probably the wire coming out of the dome light that is not connected, or broken wire leading to itIt does not work off the switch and I have replaced the headlamp switch for another issue. I checked all the fuses already. Still have not had a chance to take the kick panels off yet, it's been a little cold here. It would not surprise me if it does have other problems, she is a work in progress and isn't always the most agreeable.
do you have a dome light under the dash
Or a dome light in the fiberglass top? I have three lights that come on with the dome light switch or door switches, I'm not sure about 86 though
Believe '86 is the same. My harness is that vintage, and the floor lamp and two dome lights are in the same circuit.
I had an issue that if the floor lamp wasn't operable (bulb had a bad connection), it affected the dome lights.
I am pretty sure 81 and up have all 3 locations, under dash top and roof.I'm not sure if there is one under the dash or not, I know it has one in the roof and one in the fiberglass top
They are not in series.I believe they are all in series and all bulbs must be good for the circuit to work.