All the wires at the headlights are "hot" as in
they will all read 12V when read thru a meter
with it's neg lead grounded.
Suzuki uses a backwards approach, at least to us
to activate their electrics, it's sort of a positive ground
type system, except it isn't really, they treat the neg
like a hot or pos source would be in an American car,
and ground the wire to neg to turn on the lights, what
you are really looking for is the wire that grounds when
the lights are turned on.
I learned this trying to fix my head lights to all come on,
or rather all stay on when I turned on the high beam, I
gave up, I didn't want to hack into the electric system all
that bad.
My advice, unless you want a lesson in Japaneese electrics
is to wire the thing to a switch and be happy
Good Luck
Wild