It does sound like a ground issue to me as well.  Check the grounds that
are located behind the fuse panel.  You should be able to remove a
couple of screws and drop the panel down and you will see the ground
connections to the left.  There are a bunch and they are clustered
together on a grounding "star" connector.  Check each ground on these
two connectors and clean them as you go.  You will probably find that
one of the ends of the ground wires has broken and you will need to
crimp a new one on.  That is what I believe is going on.  The ground has
gone bad and the headlights are seeking a ground through the instrument
cluster.  You shouldn't need a new headlight switch but if you find you
need something please let me know.

Ken Wilford
John 3:16
www.vanagain.com

Michael Diehr wrote:
> 1985 Westy -- just last night started misbehaving.   Symptoms:  with
> ignition off + headlight switch on, three LEDs in the dashboard glow.
> With engine running + headlight switch off - normal.   Engine running
> + headlight switch on, all dash instruments (including lighting) go
> dead.   The load reduction relay seems to work fine (e.g. headlights
> on + ignition on = headlights work, and when you crank the starter the
> headlights go out).  Toggling high beams doesn't do anything weird.
> This sounds like a ground issue from a failing headlight switch?
> Wiggling the ignition key doesn't seem to change anything in any state.
>
> Unfortunately the van is about to go on a long trip, so need the part
> asap etc.  Are there any surefire diagnostics I can do?  I have
> voltmeter & bentley.  Thanks!
>