I'm in Maine right now and my coach is in Florida. So, I'm not able to check this for sure. Our coaches are close in the fact that they're both rear living & front bedroom.
It wouldn't make any sense for Dutchmen to place sometype of a fuse in between the fuse panel and the light. Especially where you wouldn't be able to see it (as I'm sure you already know).
Did you blow the light bulb on the light that was already there? You can try changing that and see if it corrects the problem. I'm saying that because your doing an add on. I would also, check the fuses in the fuse box. Don't rely on those little red lights for accuracy. As I found out, those fuses are not marked correctly. I blew a fuse on my furnace and it was in a different location in the panel. So, I would check all the fuses, regardless. Wish I had more electrical experience for you. Good luck!
That's cool that your adding a light in the basement. Did you place it on the other side?