When it comes to alternator operation, voltage is only one part of an
equation. What is the current being delivered. With a lot of batteries it is
possible to load an alternator down but you need to measure the current.
Above 2,000 rpm the alternator should be able to deliver close to 90 amps at
13.8 volts. Output will drop at idle.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Steve Williams
Sent: Saturday, October 10, 2009 2:21 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Another Update: Only 13V from Alternator

At 08:41 PM 9/14/2009, Steve Williams wrote:
>Just to follow up on my '84 Wolfsburg Westy with the anemic alternator ...
>
>I bought an alternator at an AutoZone in Flagstaff, just so I would
>get completely stuck over the holiday weekend.  I left it in the box ...
>
>(With the old alternator:) measured the voltage at the starter
>battery at idle and 2,000 rpm: 13.1V with the headlights off.
>
>I pulled the regulator out of the Autozone alternator ... got it
>installed (on the old alternator).
>
>I started the engine and measured 13.75V at the battery at idle and
>2,000 rpm with the headlights off.  With the high beams on, it
>dropped to about 13.5V.

Even after I wrote the above, I remained suspicious of the old
alternator, so yesterday I had GoWesty install the AutoZone
alternator, along with one of their alternator brackets.

And, oh no!  The AutoZone alternator measures only 12.8V at the
starter battery with the headlights off.

I measured 13.4V between the alternator case and the big B+
stud.  So, yes, I'm thinking of running a fatter wire to the
battery.  But shouldn't the voltage be higher?

The GoWesty tech seemed satisfied with 12.8V, but everything I've
learned about lead acid batteries tells me I want more voltage to
charge it fully!  Am I wrong?  Do we have experts on this forum, or
can someone point me to trustworthy advice on the inkernets?  What
about the deep cycle battery?

Sorry to go on and on about this.  I just don't feel like I
understand yet what the voltage SHOULD be.