Date:         Wed, 30 Jan 2002 12:40:57 -0500
Reply-To:     S Stones <sstones@IDIRECT.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         S Stones <sstones@IDIRECT.COM>
Subject:      Re: Red light rev?
In-Reply-To:  <00f801c1a94d$a4739a20$a227f140@JohnAndrew>
Content-Type: text/plain; charset="us-ascii"; format=flowed

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.