Thanks for those responses. The battery is new, and the alternator is putting out 14.7V. The only issue that I know of with the wiring harness is that there are wiring remnants of an aftermarket car alarm that I removed when I bought the truck in 2011.
I’ve mostly had the battery connected...
I recently replaced the heater core in my FZJ80. Since then I’ve been having electrical issues. First the ABS light came on, then the instrument panel illumination stopped working. The tachometer now only works intermittently. It’s not just the instrument panel—the tail lights don’t work...