normally the battery behind the passenger's seat is the primary and starting
battery,
and that's the one you'd jump start too - but jump starting is a bad thing
to do for either car, the jumper, or the jumpee, and you should really try
to avoid doing that.
  normally the other battery is the House or Aux battery.
the way I tell what's wired to what is by disconnecting each battery one at
a time.
if things are right...........disconnecting the starting battery will have
no affect on house lighting, say.
Those won't go out until the Aux battery is disconnected if things are
working right.

two other things - personally, i've never trusted isolators very much. Would
much rather have plane ole manual control of when a battery is connected.
# 2 .........be sure to never have the engine runing and no battery
connected to the alternator.
or stated in the positibve - always make sure there is a battery connected
in the circuit any time the alternator is turning .
scott
www.turbovans.com
----- Original Message -----
From: "Thomas Jefferson Kitts" <thomas@THOMASKITTS.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, July 28, 2008 11:03 PM
Subject: stupid question of the day . . .

> Yes, it's I'm a dope time . . .
>
> Got two a two battery set up in my '84 Westy.
>
> Is there an easy way to determine if they are separate power systems,
> one for the engine, and one for the living space, or wired in-line or
> in parallel? And here's the really stupid one: In the case of having
> to jump start the vehicle, which one do I attach the jumper cables to,
> the battery behind the driver's seat, or the one behind the passenger
> seat -- which of course has easier access?
>
> TIA
>
> Thomas