how do i get 12 volts to the factory installed 7 round trailer plug with elec. brake

the above is wrong on wire location. on a 7way connector, the center pin is reverse. as you look at the plug from the back of the truck, the terminal at the top right is the auxillary hot wire. there is a diagram on the connector cover. however, tennisshoes is correct that a factory plug will only have power when the ignition is turned on. if it is an aftermarket connector, the auxillary wire is frequently not connected, as it is not necessary for light or brake functions.

if the wire is not connected, you could run a wire directly from the battery to the connector. be sure to use at least 12 gauge wire and no more than a 20 amp fuse.

thanks for all the help I found the wire to have a brake in it along the framerail

I had a defective factory 7 pin connector on bumper. Power lead was not hot.