Date:         Tue, 17 Jul 2007 12:30:52 -0700
Reply-To:     David Kao <dtkao0205@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Kao <dtkao0205@YAHOO.COM>
Subject:      Re: voltaget at D+ on alt
Comments: To: Matthew <mpteleski@YAHOO.COM>
In-Reply-To:  <303012.88112.qm@web56403.mail.re3.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1

Mathew:

Well, I did not see any respone from anyone yet. So I did a little
work to check it out.

With the ignition on but not cranking the D+ terminal on my 84 has
a reading of 1.45 volt. But with the engine idling it has 14 volts.

The D+ terminal is connected through a serial resister, probably in the
instrument cluster, before it connects to a switched positive supply
from the battery. The D+ terminal is fed with a small amount of current
only before the engine is started. This small amount of current is enough
to provide sufficient magnetic field for the main alternator coil to generate
14 volt when the engine is started. Once the engine is started this D+
terminal gets the 14 volt from the alternator internally. This 14 volt
is DC because it is from the rectifier output end. The reason I think the
D+ terminal gets the 14 volt from the alternator internally is because once
the engine is started you can disconnect the battery and the engine will
continue to idle and all electricity in the van will be active still.

Well, this is how I see it. Wait for Dennis to respond. He is probably
at work and will respond later. If I am wrong he probably can correct me.
I am only trying to give you the voltages you are asking.

David








--- Matthew <mpteleski@YAHOO.COM> wrote:

> folks, what is the voltage supposed to be at the D+
> terminal on the alternator? i think i have a new
> bumbed alternator.
>
> thanks
> mp
>
> "may the four winds blow you safely home"
>
>
>
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