At 02:10 PM 12/4/2003, you wrote:
>I was looking at a way to hook the aux and vehicle batteries of the Westy
>together.  I have a charger set up on the aux batt, so that it gets charged
>whenever the vehicle is plugged in.  I would like to connect the two so
>that the vehicle batt can share in that charging when needed.  Or let the
>aux batt boost the vehicle batt when needed.  So I thought, there's already
>a relay in place to do this.  How about a little switch to energize the
>coil on that relay?  I tried applying 12V to the blue wire and that did the
>trick.  So then I started to find a switch to install for the purpose.  Now
>I am thinking about where that 12V is going to go when it also travels back
>down the blue wire to the alternator.  Is this a bad idea?  Thanks for any
>input.
>
>Edward

Use a single pole, double throw switch (SPDT).
Disconnect the blue wire from the relay and connect it to one of the switch
terminals (not the common). Connect the relay terminal (where you removed
the blue wire) to the switch "common" terminal.  Connect the remaining switch
terminal to a source of +12v.

One switch position is for charging, the other for "normal" running, with
no interaction between the two. Use a 3 position "center off" switch if you
like to also add a "relay is always off" mode.

BUT... Marks comments about safety and wire size are very valid ones
The relay should NEVER be energized during starting or severe
nastiness could occur.
At least put a fuse in the wire between batteries just in case...

Steve
EJ22 -> '86 Westy "Escape Pod"