Does your hi/low switch work as designed? In other words, when the headlights are on, it flips them hi or low in the correct position? Best thing to do is check for power when you turn the dome light on. I know on my dome light (96 Tracker) the switch doesn't always want to turn the light on. Never had the high beam indicator turn on at the same time though. Also, was the dome light working before your aluminum dash conversion? If it was a crossed wire between the indicator circuit and the dome light circuit, you'd think the dome light would still light up. So I'd start there. Make sure you're getting power to the dome lamp. And if you're not, trace the wire back. Check all your fuses of course, but there's probably a wire shorting to power somewhere. Hope this helps!
