That is a simple solenoid, the proper switch for dual batteries on the
early (air cooled) Vans. It is and Electro-mechanical switch which charges
both batteries while the motor runs, then isolates the starting battery
when the motor is off. They run about $18.00 at places that carry them.
From what I have been told, (which could be wrong) you can't use a Solid
State isolator with the older Borsch Alternators.

Zap.

G. Matthew Bulley
Director
Bulley-Hewlett & Associates
www.bulley-hewlett.com
Cary, NC USA
888.468.4880 tollfree

-----Original Message-----
From:   Bill Johnson [SMTP:bjohns@DTX.NET]
Sent:   Tuesday, November 02, 1999 2:57 PM
To:     vanagon@GERRY.VANAGON.COM
Subject:        Aux Battery Relay/Selenoid

There is an after market Aux Battery system on my 82 Diesel.  It
was disconnected from the aux battery by the PO because he was
not sure how it worked.

I see what I assume is a relay attached to the firewall.  It is
a silver canister a little larger than a 35mm film canister.  It
has 3 bolt type connectors on the right, center, and left near
the top.  The left connector is run to the + terminal of the
primary battery.  The center connector is grounded to the frame
and runs also to the - terminal of the aux battery.  The right
connector is connected to the  + terminal of the aux battery.

The wire is not a heavy gauge.  Does this sound like it is
hooked up correctly.  Seems to me it is.  I am not sure what 12v
source energizes this relay.  Can anyone give me a better
explanation of this circuit?

Bill