Dash lights turn off when headlights turned on

Previous owner had a cabover camper and did a hack job on the wiring. I’ve cleaned up most of his “improvements” but this one has me stumped.

Ignition on and headlights off, the radio and climate control are lit (as normal)

Ignition on and headlights on, the radio and climate control lights are off (just the lights -the units still function).

The instrument cluster lights never light - but that could just be burned out bulbs.

Any suggestions where to start troubleshooting this? Yes, the instrument lights are tied to the headlight circuit. but I can’t figure out what the previous owner could have done to make the radio and a/c lights turn off - they should always have power with the ignition on.