1989 Chevy Suburban electrically dead

210000 mi, 350 engine. All electrical systems died at once, except for headlights, dome light, horn. No ignition, radio, power windows, A/C fan, turn signals, wipers. Battery is charged and headlights are bright. No noises of any kind when try Start on ignition switch.

If I turn the ignition switch back to the aux position, then try electric door locks, something down under the dash buzzes (relay?). In Run position, it doesn't do anything.

With ignition in Aux position, radio works, but not in Run position.