Yes, brown=ground in VW wiring.  Probably those wires at one point were
meant to ground to one of the crown-shaped ground terminal blocks screwed
to the wall of the van, up under the instrument cluster.  My guess is
currently all that stuff is grounded only because some of it happens to be
screwed to metal brackets in the dash.  What on earth whoever worked on it
last was thinking, I don't know.  Perhaps there was a ground wire at one
point and it pulled out of the crimp connector.  You may find it dangling
up under there someday.

I would find a good ground point (make one, if necessary) and connect
those wires to it.

David Brodbeck, N8SRE
'82 Diesel Westfalia
'94 Honda Civic Si