There is a hidden fuse block in the back of your coach which has fuses for the tow hitch. One of those is a 10amp fuse for the backup lights. Perhaps it's blown. The fuse block is fun to find, on some it's in the very last bay next to the side radiator, on others its behind a screw panel in the electrical bay. You might have to do some Google work and looking around for your particular RV, as its installed differently depending on make/model, but its always at the back drivers side. I think I've read that on a 05 Meridian it's near the cable TV hookup in the bay.
Ed & Joie
2004 Vectra 40KD
Freightliner Chassis and Cummins ISC