90 dashlight problem revisited

Hi,
I know this topic is old news but Ive searched the forum and cant find any info on the 90 lumina with dashlights and heater control lights that go out when I turn the headlights on. The 90 doesnt have the fuse box on the drivers side under the hood and the fuse panel on the passenger side under the hood looks good underneath. The headlight switch is integral with the dimmer rheostat and Ive tried a used one to no avail.
Any info on this would be much appreciated.

Thanks