Date:         8 Dec 1995 20:34:11 -0800
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "Harvey Chao" <Harvey_Chao@smtp.svl.trw.com>
Subject:      Re: Alternator & O2 lights 

                      RE>>Alternator & O2 lights on                12/8/95


>My van does this everytime. The lights go off after a certain rpm and 
>do not come on again. I've heard this is normal and has something to 
>do with the field voltage in the alternator or some such (someone set 
>me straight).

My interpretation of Steve's input above is:

When I start my van the red alternator light remains on until the engine revs
climb above idle, either when I "blip" the throttle, or when I accelerate to
drive off.  (personally, I have a diesel, so there is no "fast idle" when I
start a cold engine, idle speed is always the same).   Steve is pretty close
to the mark as I understand the alternator/regulator circuits.  These are
"self exciting" alternators, depending upon residual magnetic field storage to
"bootstrap" the device into the generation of electricty when you first start
them rotating.    I think (gimme so slack, it has been almost 30 years since I
took that course (that I hated) in rotating machinery) that the output builds
up with rpm until it can generate enought voltage to energize it's own field
windings, and then the regulator can kick in and do it's thing.    Anyone out
there that can confirm or (better yet) correct this?
Harvey