Okay, I've seen some strange things during my tenure as a Vanagon owner,
but this seems even more odd than normal.

When the van is hot (ie, on a hot afternoon/evening or after a 25 mile
drive on a warm morning) the tachomteter becomes very inaccurate.  Or it
doesn't work at all.  The needle never seems to show a number higher than
I'd expect, but it's often lower.  Frequently it just sits at 0.  When I
hit a bump it might swing all over the place.  This only started happening
within the past week or two.

Any ideas?  I'm at a loss.

--jay