Take off Hi and Lo wires at dimmer, leave the hot wire on, turn on headlights, see that dimmer terminals show hot on each terminal as you push the dimmer switch, and that the indicator operates correctly. If all is good there, then obviously the problem is after the dimmer.
Then run temporary wires from the two dimmer terminals directly to the bulb terminals. No connectors involved. No new harness wires, no old wires. Bypass the terminal strip. You see the method here? Bypass everything and use new jumpers to isolate the problem. If you get success, you gradually put it back together until problem reappears. Bingo! you have isolated the problem. To isolate a circuit component you eliminate it/bypass it to observe any change.
It seems like a lot of work but it is THE fastest way in this case. Just get some long pieces of wire not used on the harness or what you have laying around.
The dimmer terminals and the bulb terminals may have standard 1/4" blade contacts which accept a 1/4 female crimp contact for your test wiring.
