Many thanks for the on- and off-list suggestions: ignition switch,
Hall sender, and loose things in the fuse box area.  It doesn't seem
to be the Hall sender (i.e., it's intact, seems well fastened, seems
to pass the multimeter test).  I'll look for loose things in the fuse
box area; I'll even try to find places to attach the ones I find...

I once tried to take out and replace an ignition switch.  After
breaking the existing switch while trying to take it out (and I think
I broke something it attached to), I wasn't really satisfied with my
subsequent installation of the new switch.  I've tried a "search
ignition switch in vanagon" in the archives, but I don't get anything
that says "here's the idiot's step-by-step HOW to take out the
ignition switch and to put a new one back in".  Any guidance?
(please??)

Thank you all again!

Chris