Date:         Thu, 31 Jan 2002 16:11:56 -0800
Reply-To:     Alistair Bell <albell@UVIC.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Alistair Bell <albell@UVIC.CA>
Subject:      Re: Red light rev
Comments: To: David Beierl <dbeierl@attglobal.net>
In-Reply-To:  <5.1.0.14.2.20020131172510.02a6dc50@pop1.attglobal.net>
Content-type: text/plain; charset="US-ASCII"

David et all,

I've wondered wether the long (relatively) wire run from the alt to the
dash, and the (most likely) less than perfect connector just forward of the
pass. side tail light would contribute enough resistance to raise the
required "excitation" rpm.

Alistair


on 31/1/02 2:34 PM, you  wrote:


> 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
>