David and Andrew,
      Might not this deliberate design choice by VW be
to prevent drag on the starter motor from the
alternator during start up?   Could make the
difference in those cold Rhode Island winters as you
crank away?    "Better to light a red light than to
curse a nonstarter"    gary

>Andrew,
>       I may be wrong about this but I do not think
>there exist a permanent magnet "weak or strong" in
the
>alternator.   Increasing the engine rpm turns on a
>electrical loop from the dash that provides power to
>the alternator thus making the electromagnetic force
>needed to make the alternator charge.   The bearded
>guy from back east can explain this better than I.
>The jolly guy from cape cod.   regards gary

Glad they're not talking about me (the cranky guy from
Rhode Island).
<g>

But FWIW, you're right.  The old DC generators had a
residual core
magnetism that was necessary to remind them which
direction to charge
in,
but alternators (except the "self-exciting" type) rely
on an input
current
on the D+ terminal to energize the field enough to
begin charging.  The
rpm
at which this happens appears to be dictated by the
amount of current
you
supply to the D+ terminal, other things being equal.
So it appears to
be a
deliberate design choice by VW when they specified the
bypass
resistance
that parallels the LED in the panel.  Hanging relays
on that line ought
to
raise the required rpm by diverting some of the
current intended for
the
field (though probably not by much).

Ref. Bosch Automotive Handbook p. 809ff.

david

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

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