At 07:03 PM 6/17/2011, Jim Felder wrote:
>My brother and I were talking about how to wire it and we came up with the
>idea to wire it into the trailer pigtail backup light. But, it turns out,
>there isn't a backup light wire so that is not an option. The idea was to
>get a trailer-side connector for when the light was in use. I suppose I
>could tap into the running lights, but that could be awkward in some
>situations where you wanted to be able to turn the light on and off. I also
>thought about running a wire from the backup light switch, and having some
>kind of a pigtail available cable-tied to the hitch bar, say. It would suit
>me fine if, say, the light was on when the car was in reverse and the light
>was plugged in. I don't see operating it with a dedicated switch.

Get two two-terminal trailer plug pigtail pairs like these:
http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=109505&catalogId=10001&langId=-1&storeId=11151&storeNum=10109&subdeptNum=10611&classNum=10615
.  Wire your light to one end of one.  Toss out that same end of the
other one or use it somewhere else.  Wire the *other* end of one pair
to a lighter plug, making sure that the negative terminal is exposed
on the lighter-plug side and buried on the lamp side.  Now take the
corresponding one from the other pair.
Run a fused circuit from the B+ post in the wiring box to the 30
terminal of a relay that you stick in the box.  Tap into the switched
side of the backup lights for the 86 terminal and ground the 85
terminal.  Extend your two-pin trailer plug so you can reach it along
with your regular trailer wire.  Wire it to ground (exposed pin) and
to the 87 terminal of your relay.

Now you can plug in your lamp and it will operate together with the
backup lights without overloading the backup switch.  To use it in
other places, plug it into the pigtail you wired to the lighter plug.

Yours,
David