The AC runs through a 30A gray Square D breaker box usually with one 20 A breaker for outlet and the light
over the sink. Usually white Romex cable
12DC: The battery+ (black wire) has a 20 amp fuse this wire hooks to the 12V tow vehicle wire. The house wiring also a black wire with a 20 Amp fuse runs through the rest of the trailer with a white ground wire. Your all your loads just parallel off of these two wires, usually with scotch lock connectors. The house 20A fuse is usually located just as the wiring harness comes into shell under the front bench.
I usually install a Blue Seas fuse panel (6 fuse) and split the frig., furnace
ckts. I also add a 7 lug terminal box to attach your pigtail and running lights
The running lights
use the Bargman trailer wiring code. as in the new wiring diagram. This color code is also used for molded pigtail TV cables.
Besides your running lights the blue wire is your brake wire.
I can't find the old wiring diagram either.