Before you start removing panels open the effected receptacle closest to the ac panel and locate the feed fire coming from the panel. This can be do by turning the power on and testing the black and white wires of each of the cables coming into the wall box. If you see power on a pair of wires the problem could be a loose connection on the receptacle you just removed to do the test.
If you do not find power go to the inside of the ac panel and make sure all connections are tight there and retest.
If both tests fail the wire itself is broken somewhere in the walls.
If this is the case you can go one step further. Remove power from the trailer and lift each wire off the fuses, you do not have to lift the white wires off the neutral block. With a length of wire long enough to reach from the ac panel to the receptacle test for continuity on each wire in the receptacle back to the wires in the panel. You should be able to locate at least one side of the wires in question, as it is unlikely that both sides will be broken.
If you can only find one side as good then you are in for some panel removal and rewiring.
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