Does this help:
http://www.globalserve.net/~jrivers/aux-batt.htm

and, or this:
http://www.geocities.com/harald_nancy/dualbattery.htm

bob

----- Original Message -----
From: "Jeff and Jen Gilbert" <jeffnjen@JEFFNJEN.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, May 15, 2004 12:32 PM
Subject: Aux Battery Wiring

> I am about to install an optima behind the drives seat in my 87 camper
> (manual trans).  I wanted to make sure everything was working correctly at
> the relay before spending the buck fitty on the battery (PO had an aux bat
> set up by rear heater which died, so I removed it long ago with all the
> wiring).
>
> The wiring seems correct according bentley (97.34a).  Here is what I have
> with engine running:
>
> 30 - thick red wire, 13.8v
> 85 - small black/red wire 0v
> 86 - small blue wire 13.8v
> 87 - fat pinkish/red wire 13.8v
> center connector - fat red wire 13.8v
>
> Does this seem correct?
>
> Thanks,
>
> Jeff
>