Depending on the year of your vehicle and the type of connector that may or may not have been installed by the factory, you could have a "hot" wire already running to the trailor, normally about a 10 ga. this is for running interior lights and the like.
Are you running a ground from the trailor to the truck, or are you relying on the trailor hitch to make the ground, if you are relying on the hitch this will kill the brightness of the lights on the trailor.
If you decide on running your own hot wire with a relay make sure you fuse that thing right up close to the battery, beleive it or not, I have seen a couple of vehicle fires, because of modified wiring that shorted with no fuse to blow.
Hope this helps.
Are you running a ground from the trailor to the truck, or are you relying on the trailor hitch to make the ground, if you are relying on the hitch this will kill the brightness of the lights on the trailor.
If you decide on running your own hot wire with a relay make sure you fuse that thing right up close to the battery, beleive it or not, I have seen a couple of vehicle fires, because of modified wiring that shorted with no fuse to blow.
Hope this helps.