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
Date:    Wed, 30 Jan 2002 12:40:57 -0500
From:    S Stones <sstones@IDIRECT.COM>
Subject: Re: Red light rev?

At 10:19 PM 1/29/02 -0700, you wrote:
>Hi,
>Just something I have been wondering for a while.
Why do you need to
rev
>the engine to get the alternator to start charging
the battery and
hence
>to get the charging light to go out.  It seems this
is a symptom
peculiar
>to Bosch systems.  My vehicle at work, a Kassbohrer
Pisten Bulley Snow
>Cat, has a Bosch system as well and performs the
same.  Anybody out
there
>know why?
>TIA,
>John Andrew
>1984 "Westiico"

The relatively weak permanent magnets in the
alternator are not capable
of
generating the 12.5+ voltage neccessary to start
everything charging up
until you get the alternator spinning fast enough...
Once spinning fast enough to develop higher voltage
the rotor windings
are
charged and providing a strong magnetic flux (So that
it can keep
everything up at lower speeds). But until you get the
rotor windings
charged up, the little permanent magnets need the help
of a good spin.

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