I'm starting to wonder more about the spotlight. I want to dig into the dash a bit anyway because one or both of front speakers is crackling and annoying me, so I'm going to dig in a bit and follow that factory spotlight wiring and see where it leads. I've had everything out before to bare firewall, and just can't remember now, and whether there's inline fuse. I still need to test alternator too.
If you suspect the spotlight,
and do not want to tear into the dash
begin by disconnecting the two battery cables
remove the bulb from the spotlight
and use a good meter to measure resistance in Ohms
from positive + bulb socket contact pad to black - battery cable.
Using a “Megger” meter hand cranked at a higher voltage than the 9 volts of the typical multimeter would be even better.
https://www.youtube.com/watch?v=t0k8MnJzM_ghttps://www.youtube.com/watch?v=WpANiRvB4tE
