I just went and studied the pictures a little longer and now I think I understand better what I am seeing.
The box in the bottem of the closet is directly above where the 120volt ac wiring comes into the trailer.
It goes to this box and then branches up to the two outlets in the side of the closet that we can see the rear of and then onto the outside
light as we can also see the rear of that box.
My 1300 did not have these three boxes and they do look newer than the trailer to me.
The next thing is this....under the cover plate of the box in the closet bottem where the wire comes into the trailer there should be three wires.
-One feeds the trailer from the cable outside.
-another feeds the circuits we just spoke of and can see in the pictures
-the third(if it is like mine)goes under the step up for the bed/table and to the sink side of the trailer. On mine there is an outlet on the side of the sink facing the seating are(a strange location) and then it goes onto the fixture above the sink which I also had but forgot I had removed.
What I am getting at is that you should be able to see the 120volt ac at box in the bottem of the closet first.
If it is not there then I would suspect the cable that feeds the trailer has a problem,not hard to beleive for a 30+ year old cable living outside much of the time.
If there is voltage there then look to the connections to the wire that leave that box heading for the other two circuits. The newer one that is fully exposed inside the closet should be easy to trace as you see and touch it for its entire length.
The one that goes to the sink side may not be as simple but I don't really think you problems are there anyway.
My guess is that somewhere where the cable comnes into the trailer it is broken or the connections inside the box in the bottem of the closet are just bad and broken.
Be careful here too as these voltages can kill.
I hope this made some sense.
Please let me know if not.
Ed