Date:         Thu, 13 Nov 2008 22:52:47 -0500
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
Comments:     RFC822 error: <W> MESSAGE-ID field duplicated. Last occurrence
              was retained.
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: Thanks on the amps/voltage explain..
Comments: To: Don Hanson <dhanson@GORGE.NET>
In-Reply-To:  <000701c945b6$56d47b60$4001a8c0@gateway.2wire.net>
Content-Type: text/plain; charset="iso-8859-1"

It is called excitation, getting started or kicking in.

Basically alternators or generators work by moving a magnetic field across
the windings. In an alternator, the windings that produce the power are
the stator. The spinning magnetic field is provided by the rotor.

When the ignition is turned on, the current that lights the dash indicator
is completes the ground path through the rotor. This provides some current
and a small magnetism. When you rev the engine, the magnetic field will
produce current in both the stator and feedback through the rotor also.
This back feed is what will turn the light off and the alternator is now
kicked in and charging.

The light bulb is important as if it was not there, the back feed will
keep the ignition circuit energized when the key was turned off.

The campers with the fridge control relay add a bit of complication to
this as the relay is added to this circuit. If you disconnect the blue
wire to the alternator the light will stay on but the alternator will not
kick in until some high revs are reached or not at all. Note that the
relay ground is to the starter solenoid. Why? While the starter is
energized, the 12 volts from the key will back feed. As the engine starts,
that brief moment between starting and the key being released will help
get the alternator kicked in as the load of the relay coil will be
cancelled out.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Don Hanson
Sent: Thursday, November 13, 2008 12:36 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Thanks on the amps/voltage explain..

  I learned something.  Slowly, electrical become a little less strange to
me.  I have a text I am actually reading on Marine Electrical
systems...Should have done that years ago..

   Here's a silly question:  When I start my Van (inline 4 motor, same
alternator as  a Vanagon,  if that makes a difference) the alternator
light
comes on, as it should. It stays on until I rev the engine once, then it
goes off and stays off.  Why?
  Just curious..it works fine, just strikes me as odd the light will be
off
at the same RPM once you rev it and let it drop back down.
  Don Hanson

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