Center Pin on Pigtail?

Im trying to find out how to get a hot wire to the center pin on the pigtail. It will be used for an axle lift on the trailer. Mine was not originally wired with a switch on the dash for an auxillary power source to the trailer. Any ideas what wire I need to tap in to? I know the old freightliners were easy...just tap into the blue wire and you were good to go. I love this truck, but the wiring has left much to be desired. Its really just a confusing mess! I would appreciate any help!

 

Thanks for the reply. A buddy called me and told me that very same thing...I didnt realize that since all of the trailers I have pulled so far are 97 or older. I checked wiring and discovered a break just before the pigatil recepticle. I think what Im going to do is splice in there, and run wires up to the cab from there with a switch in line. South Dakota doesnt have any laws pertaining to in-cab lifts. The truck is a 99. Thanks for the help.