I have two 12 volt circuits fed from the fuses under the electrical center. If the wiring was damaged, causing the fuse to blow, then you really need to trace the circuit starting right at the panel. My guess wherever the wire runs in an area subject to something coming into contact with it, like under the dinette seat, etc.., or where it maight have been damaged at a turn or fastener, would be the culprit. If you can't visibly trace the wiring, I'd try going fom device to device with a continuity tester until the bad section was located. Just replacing the bad section rather than fooling with it is sometimes faster and easier. On another note, I had a similar problem with the 120 volt outlets. The GFCI outlet had activated and turned off power to the devices on the same circuit. In my rig, there are two circuits, one serving each side of the rig, each with the GFCI recepticle first in line to protect each circuit. the solution it to trip and reset all your GFCI outlets, and the power will probably restore.