new update... I did some tests while the bus was running. Like you said the voltage at the switch matches the battery when the marker lights are off. When running, the battery terminals and the switch both were at 14.1 volts. When I turn the marker lights on, it ALSO matches the battery but there is a drop. At the switch and at the battery it is 13.6 volts.
Just incase that didn't make sense...
Bus running at fast idle - Marker lights OFF - Switch = 14.1 volts
Bus running at fast idle - Marker lights OFF - Battery Terminals = 14.1 volts
Bus running at fast idle - Marker lights ON - Switch = 13.6 volts
Bus running at fast idle - Marker lights ON - Battery Terminals = 13.6 volts
I ran 12 gauge wire which I've been told was more than enough. And when I say I ran new wires, I simply ran them from the side driver panel junction box, all the way to the rear lights, I didn't rewire all the markers themselves and I also didn't rewire from the battery to the junction panel. But rewiring the parts I did increased the voltage to the tail lights by almost 2 volts.
What are you guys thoughts on this? Thanks!!!