I had similar measurements, and changed out the ground cable from the battery to the body (and replaced the corroded old ground screw with a shiny new stainless).  Increased my voltage by a half-a-volt.

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Don Hanson
Sent: Thursday, February 03, 2011 12:29 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: alternator output question

  OK, so I went at the connections and cleaned everything up while I had the decklid off to check the alternator numbers.

  I got these readings:  At the starter battery...with the secondary circuit turned off...

   At the starter battery 13.48v (13.68 after cleaning up the connections)
   At the alternator        13.82  (13.98 after cleaning up the connections)

  The readings didn't change much when I turned on the lights....I didn't re-do that test to get actual numbers, but when I was at the Auto parts
(NAPA) having the guy check the new Aux battery I just got (one week old) we did do that test with his instrument on the battery..the starter battery too..and there was little change in the alternator output....

   The only other thing I can think of is my ground connections...I have an extra from the block to the chassis as well as the tranny one...those have not been cleaned for about a month is all.

  Don Hanson

On Thu, Feb 3, 2011 at 11:44 AM, Scott Daniel - Turbovans < scottdaniel@turbovans.com> wrote:

> what is the voltage at the alternator main post ?
> ----- Original Message ----- From: "Don Hanson" <dhanson928@GMAIL.COM>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Thursday, February 03, 2011 10:43 AM
> Subject: alternator output question
>
>
>
>   My bosch alternator,  a rebuild  just a few years old, is giving me 
> 13.10
>> +/- volts at the passenger side (starter) battery terminals.   I am
>> thinking
>> "new Voltage regulator"...right?  When I add rpms or load (turn on
>> headlights)  nothing much changes with the voltage.  anyone care to 
>> comment or confirm that another regulator is the 'right stuff?"
>>
>>  Don Hanson
>>
>
>