I am pretty sure I know what it is.  There is a fuse that diesels have on the
fire wall for the starter and glow plugs.  It is usually a little black box
with a red wire going in one side and out the other.  Take the cover off and
you will see two screws and a fried looking piece of metal in between.  Your
local VW dealer should have another and since they are cheap, buy a few extras
and put them in the van just in case.  Hope I helped ya.
Ken Wilford
John 3:16