I've always been curious how the wiring is routed. Is it embedded in the cabin top, or is there some sort of conduit or channel? I wonder if a tone generator circuit tracer tool could trace the cable routing to help find an access point. https://www.amazon.ca/s?k=tone+generator+tracer
On the chance that its just a bad connection somewhere: The wiring diagram shows that the head light positive wire is connected to a main wire that then goes to the chart table light and then the port side salon light before going to the electrical panel. I assume those other two lights are working? The connection at the chart table light might be a good place to check continuity to since its easily accessible. Check for continuity from the head light positive wire with the breaker off.
It looks like the negative wire goes directly to the DC negative buss bar behind the electric panel. Another continuity test you can try.
/Jeff
On the chance that its just a bad connection somewhere: The wiring diagram shows that the head light positive wire is connected to a main wire that then goes to the chart table light and then the port side salon light before going to the electrical panel. I assume those other two lights are working? The connection at the chart table light might be a good place to check continuity to since its easily accessible. Check for continuity from the head light positive wire with the breaker off.
It looks like the negative wire goes directly to the DC negative buss bar behind the electric panel. Another continuity test you can try.
/Jeff