After ordering a new switch from BJ’s Offroad (a useful and well-stocked supplier of FSJ parts and accessories in Washington), Carl and I went back to work on the fog lights in the carport this evening. Carl had come up with the electrical wiring diagram for the headlights to compare. Using his meter, we confirmed we had power to the switch at the harness (but the old switch didn’t work, hence the new one), and we knew the lights themselves had good wiring.
Still, even with the new switch in place, we had no fog lights. That left the relay that sat between them to test. Carl popped it off, reading he schematic printed on the side as if he were an archaeologist interpreting an ancient rune. After figuring out which of the five prong was which (and consulting the wiring diagram printout), he went back to work with the ohm meter, confirming the relay worked–in theory.