This sounds like the type of switch typically used in dual battery setups
for boats. This is an excellent, although seldom used, option for
automobiles. The main reason for this is a lack of contact between folks who
inhabit these two, different, worlds. No way to answer your questions as to
the circuit, as that would depend on what was on the mind of the installer.
It could be wired in one of several ways. In marine applications, the
purpose of this is to select the battery you want to use to power auxiliary
loads, while reserving the other to start the engine. If both are depleted,
you can connect them in parallel, and hope that the resulting power is
enough to start the engine. Not nice to run out of battery while drifting
about, and not be able to start 'er up. This is only a switch, not an
isolator. Chances are that you have one of those also. Sounds like you need
to find a competent automotive / marine electrician to check out your
system. Of course, one other possibility is that both of your batteries are
shot.
Chuck
'83 Westy
-----Original Message-----
From: Rodney Woten <rodney.woten@LENNOXIND.COM>
To: vanagon@GERRY.VANAGON.COM <vanagon@GERRY.VANAGON.COM>
Date: Thursday, July 11, 2002 3:28 PM

Another quick question to throw out to the group.

My van has a rotary battery switch to control its dual battery setup.  It
was installed by a previous owner in the cabinet under the sink.  The switch
can select battery 1, battery 2, both or none.  Is this a genuine VW
accessory, a Bosch accessory or some other aftermarket accessory???

Anyway, I've been having problems with both of my batteries dying and
wondered if it's not the cause.  My question is,  Does the starter always
pull from battery 1 (primary battery) regardless of the switch position???
I'm under the impression that all this switch controls is where everything
except the starter pulls juice from (accessories and the like).  Does this
switch isolate my primary from my auxiliary battery so that the aux. doesn't
draw it down when it's low????

Thanks in advance!!!!
Rod Woten
'87 Westy "Wally"
Des Moines, IA