High beams

This is a simple circuit. Power to the headlights comes from the light switch, goes down to one terminal of the dimmer switch. It simply switches between high and low. Each wire, high and low, then feeds out through the bulkhead connector to the headlights. Most years have a common ground. It's not unheard of to blow up two lamps at the same time. Wiring diagrams and factory service manuals are free, over at MyMopar. Some of them came from the guys on here.

The high beam indicator is fed (branched) off the output of the dimmer, so if the indicator is working, so is the dimmer switch. All this leaves is

the bulkhead connector terminal

the actual wire to the headlights

the splice feeding to the two high beam filaments.

and the high beam filament in the lamps themselves