see if you actually have 12 volts at the plug on the jeep with your voltmeter. it's wierd that it's both sides. maybe the wires are chewed if they go all the way up front. my trailer lights are wired to the tail lights directly, and the ground comes off the frame. i run a 7 pole plug and have electric brakes as well as accessory power for reverse lights. i use copious amounts of dielectric grease to avoid flickering. don't let someone else install a new harness, do it yourself. you know where the wiring has to go to keep it in one piece, they don't care.