Date:         Fri, 26 Sep 1997 07:38:05 -0700
Reply-To:     "Michael A. Radtke" <m.radtke@ELM.AZ05.BULL.COM>
Sender:       Vanagon mailing list <Vanagon@Gerry.SDSC.EDU>
From:         "Michael A. Radtke" <m.radtke@ELM.AZ05.BULL.COM>
Subject:      Re: Battery, OXS lights stay on after start

Hello,

This is normal, but perhaps different for every vehicle since some seem to
do it and others not.

The vanagon alternator is self exciting.  In other words, some residual
magnetism remains in the field after the last time the engine was run.  On
the next startup, this tiny residual field is generates some small
alternator output.  When that output is high enough, it is fed back into
the field windings and the field gets a little stronger, etc., until the
alternator reaches full output.

How much output the tiny residual field generates is of course related to
how strong it is, but also to how fast the alternator is spinning.  So, if
the residual field is fairly strong, just idle speed gets the alternator
"bootstrapped."  If it is weak, perhaps a small throttle blip, bootstraps
it.  If the residual magnetism is very low, perhaps 2000 rpm or so is
necessary.  In all cases, once the bootstrap has occurred, the alternator
works just fine.

My '84 takes a blip after 24 hours or so, but idle is enough if driven more
frequently than that.

However, if my alternator took 2000 rpm to bootstrap, I would replace it.
 Not because it wouldn't keep the battery charged, but because of the
annoyance factor.

Mike


Michael A. Radtke  -  Z74               Voice: 602-862-4897
Bull                                      FAX:         4853
13430 N. Black Canyon Hwy.
Phoenix, AZ  85029                      Email: m.radtke@bull.com