I had the same problem on my TT. Take off the vent and the inside flashing.. take the light off the ceiling.. using a thick wire make a hole in the foam insulation going from the vent to the light. Once it is through tape appropriate gauge wire to the "fishing wire" and pull it through. Actually easy but can be a little frustrating.
2004 Chev Silverado Duramax optioned past the max. 2009 Jayco Eagle 308 RLS 765 watts of solar, 6-6 volt batteries (696 amp hour), 2000 watt (4000 surge) whole house inverter.
140 days boondocking in 2016
211/2015, 196/14, 247/13, 193/12