Relay (NAPA is fine.  Tell 'em what you're doing and they'll get you
the right one. My NAPA says E-123):

five terminals. we'll call them A-B, C-D-E

Terminals A-B go to the electro-magnet that closes the C-D-E switch.

So....
A to wire to existing backup light wire
B to ground.

Now when the existing backup lights are lit, the electro-magnet closes
the switch.

C to 12v source.  The big terminal on the alternator would work.
D & E to new sooper-dooper backup lights.

and when the electro-magnet closes the switch, circuit C-D-E completes
and voila! let there be light.

Jim

On Sep 20, 2009, at 11:52 AM, Robert Stewart wrote:

> I was not planning on using a relay since there is an inline fuse
> which I assume would blow in the event of an overload.
>
> I have no idea how to use a relay with the backup lights.
>
> Where do I get the relay? Autzone, Napa? What kind?
>
> How do I wire it properly with the relay so that when the reverse is
> engaged the aux backup lights will go on.
>
> Is as I outlined just with a relay in between the black/blue wire to
> the Green wire?
>
> Robert