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The first thing I would do here is to go to one of the switches and take it out and check to see if you have good DC voltage to it. That would take a small digital mutimeter or at least a 12 VDC test light. Ground one lead of the meter or test light to a good ground nearby and check for power. IF you have power, then chances are good that the ground side is the problem. Most of those items in the ceiling share a common ground. Test that theory by adding a test ground lead at one of those items not working. IF they all come on, then you have the answer. Hope that proves helpful here. Please get back to me if you need more as all follow ups are included in our fee.
So you eliminated some of the possibilities here. I don't believe that there is any other fuse. You might contact Thor and see if they can furnish some wiring diagrams for this. I am attaching a link to that for you. Can you attach a photo of your distribution panel or at least give me the make of it? http://thormotorcoach.com/contact
Good job on the photos and wiring diagrams! Those diagrams look to be upgrades for just some of the circuits from what I can see. The load center has the upgraded version converter which is good. So.........all those circuits have individual fuses for each one. They usually share a common ground. IF you are sure that when you hooked up the test ground back to the converter ground that you still showed no DC power on your meter, then something must have interfered with all those in one place. Any possibility for some kind of damage any place? Any evidence of squirrels or mice? Just pretty strange that more than one circuit is affected here. Most of those go across the ceiling.........any damage to the roof or possible leaking? Those would be things to look for.
IF all those circuits go into one plug someplace along the line................chances are good that it is loose or unplugged.
A call to Thor Technical Service may shed some light on the actual location of that plug............
In the shop, we would have to track down the plug for that in the harness OR call for help. We don't have much available in manuals from many manufacturers. They make up these looms and use plugs to connect them together. I think that is where the problem is. You just have to locate that plug. It could be any place, but hopefully it is accessible.
Let me know how it goes........but, this would only be a temporary fix. If that doesn't work, you pretty much know it is a plug.
I suppose, but that might take some doing.