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 ------------------------------------------------------------ + To unsubscribe from the Vanagon List send an e-mail to + listserv@gerry.vanagon.com with SIGNOFF VANAGON + in the body of the message. ------------------------------------------------------------ ------------------------------------------------------------ + To unsubscribe from the Vanagon List send an e-mail to + listserv@gerry.vanagon.com with SIGNOFF VANAGON + in the body of the message. ------------------------------------------------------------ |
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