Yes the wireing is down the drivers side and then cross to the passangers side but the crossover is up inside the bellypan not inside the axles. That makes it a bit hard to trace.
If you can drop the edge of one of the belly pan panels just forward of the front axle you might be able to see the connection to the passanger side. If you do not want to drop a panel consider running a new wire from the tongue toeach of the passanger side brakes. wires that I run under the trailer I run inside 1/8 in tubing for protection.
If you run new wiring consider installing a 10 amp fuse on each side if you have 2 axles. Magnets draw about 3 1/2 amps per so 10 amps is a good choise. This is especially a good idea if you do in fact have a broken wire in the body that you have not located and capped off as it may short in the future and cause you to loose all brakes.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles