It's the connector for a magnetic pickup used by VW diagnostic gear to
detect ignition timing.  The wire goes to the flywheel housing where there
is a coil assembly -- there's a little tit on the flywheel that triggers
it.  No earthly use that I know of (I *think* the VW gear is obsolete and
no longer used).

david

At 10:54 9/27/2000, Jean-Guy Savoie wrote:
>Hello one and all
>
>I have a 1.9l WBX 1984 with a 90A Alternator.
>
>The MYSTERY: there is a wire with a small round four pronged (male) plug
>(larger round than a pencil, smaller that a dime) mounted on top of the
>alternator (it ends at the the plug, that is not connected to anything else,
>prongs inside rubber sleeve pointing to driver's side).  This wire comes
>from beneath the passenger side air intakes and I can't follow it any
>further.  It APPEARS to go into the crankcase at the juction with the
>passenger side cylinder bloc, but that can't be right.

David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"