Parking light position works fine. Headlamp position produces no headlights, parking lights, or dash lights, but high beams come on if hold dimming stalk in. 15 amp fuses fine; new bulbs gave same result. Any thoughts would be appreciated.

 

Main switch is likely bad. Mine did the same thing but had a few warnings, like reverse lights not working sometimes. The switch was coming apart from the back. I pulled it out, opened it, made sure everything was placed properly, and super glued it together and had no more problems.

Carefully pull the panel out then unplug the switch and remove it. Then set it on a table or something and check it out. It's about that age, plastic just starts coming apart, especially if you twist and pull on it.