Did you ever find your problem? I'm late on the scence here and you may have left already.
On the 2004, T2499 the wire pack for all the rear body lights and tail lights is under the camper by the hot water heater. Crawl under and look up you will see the wire pack. It then sneaks up under the Darco and up the wall to the lights.
There is a frame ground there that is most likley corroded to death that feeds the rear camper DOT lights.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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