... when I check the voltage on the wires running to the bus lights, they are only 9 volts, doesn't matter if it's markers, blinkers, breaks, etc, it's all 9 volts. To eliminate a ground issue, we run a wire directly to negative terminal of the battery to the ground at the lights, still only 9 volts, we then ran a wire directly from positive side of battery to the lights and got the full 12.5 volts, and the lights got a lot brighter. This means somewhere between the battery and my tail lights, I'm loosing voltage.
We ran a jump wire from the switch all the way back to the junction box and got some increased voltage. Is this am ok thing to do? I didn't know if there were relays or anything I'm bypassing that could cause an issue.