I have power from the Nav switch, bulbs are good. When I pulled the bulbs out I checked ground at the socket, left and right sides are good however the center pole is also grounded which you would think would pop the breaker, it does not. It appears that the single wire from the switch is either split from a butt splice or terminal strip somewhere. I opened the wing fillet panels, now I have to I.D. the Nav wires, also need to pull off wing tips to see what's going on with the socket, I have ordered the thumb drive, thanks for the Link. BTW I have heard that when checking for ground if you leave a bulb in the socket on the opposite side the center pole will show ground because its completing the circuit. I had both removed and also disconnected the feed wire at the switch because the switch is lighted, center pole still shows ground. I'm somewhat decent electrically but not an expert, just a process of elimination.