You completely missed my comment about that "sweet spot". That is not normal operation and is not a valid test. It only shows the rear bulbs and wiring to them are okay.
The only way to do diagnostics in the circuit is to switch it to the position that does not work as designed, then analyze the voltage readings. You found no voltage on the tan/black wire that feeds the tail light circuit, so of course that circuit will be out. Pulling the switch half way out is connecting the tail light circuit to the wrong feed circuit. That is a function of the location of the contacts within the switch.
You need to find out why 12 volts is missing on the tan / black wire. You said the fuse is good. That leaves a break in the wire between that fuse and the switch, or, as ASEMASTER6371 said, 12 volts is missing to that fuse.
You said, "This concern of mine is hard to explain. My lights they all work, I am getting proper voltage, my fuses are good, ... ", but earlier you said you had 0 volts on both the tan/black and the black/yellow wires. Both of those statements cannot be right. You do not have proper voltage, and the lights do not work properly. Measure the voltage on both sides of fuse 17 and tell me what you find.
Tuesday, December 26th, 2017 AT 2:16 PM