Based on everything Iíve read, hereís the layout of your current fuse box:
Basically, the two fuses protect the battery and trailer from each other. They are there mostly in case you hook the battery up backwards.
The converter feeds the red wire coming into the fuse panel at the top grommet on the right side. The black wire most likely goes to the umbilical cord to the TV. The two white wires in the second grommet also go to the converter and the TV. Only place they make sense to go to.
The big wire nut is your ground bus. All the 12 VDC commons are tied together in that wire nut.
The black wires feed the cloth covered wires youíve found, which must go to the lights, furnace, and old pump location. The only way to know for sure which is which is to disconnect them from the distribution block and either use your ohm meter to see which wire is which, or to disconnect them one at a time and see where you lose 12 volts at the other end of the wires.
As far as I can see, there are no fuses between the converter and the 12 volt
circuits. That is not good, and there is nothing to protect the wiring, or your converter, other than the internal circuit protection your converter may have.
If this where my trailer, Iíd replace the old distribution block in this fuse box with a new 4 circuit fused distribution panel like you installed in your other trailer.
Do you know the gauge wiring that goes to the converter? That would be the thick red and white wires. It looks like the red, black, and two thick white wires are all the same size, is that correct? They might be 10 gauge, but Iím guessing on that.
How far away from this distribution block is the new converter? Distance in wire feet if you can figure that out. A close approximation would be fine. Asking in case I want to change my suggestions below.
Hereís my suggestions:
Install the converter in its new location. Assuming that this is 10 gauge wiring, install a 30 amp inline fuse on the positive output of the converter at the converterís location. That will protect the rest of the wiring in the trailer.
Install a fuse block to replace the old distribution panel. Use the 12 volt
input lug to connect the converter and positive battery fuse to the fuse block.
Run the 3 12 VDC black wires to 3 fused circuits. Use fuses to correspond to the black wire size. 15 or 20 amp depending on if the wires are 14 or 12 gauge.
Connect the black wire from the TV to the 4th fused position on the fuse black. This will add a fuse into the TV circuit. Use a 30 amp fuse if the wire is 10 gauge.
Use the two glass fuses already there to protect the battery. 30 Amp would be good if those are also 10 gauge wires.
That all make sense?
To answer some of your other questions:
1. Why can't I just connect a 12V
wire (12 gauge) to the existing water pump wire (black) and run it up to the front where the new water pump will be? That way the switch would still work for it, wouldn't it?. Yes
Would I need to put a 20 amp in-line fuse in the wire just to be on the safe side?Not if you use a new fuse block.
What I don't know is what do I do with the white wire? Connect it to the skin? Connect another white wire to it and run it to the front where the pump is? And then do what? Do as TG said Ė connect a new white wire to it and run to the pump to provide a ground/common return for the pump.
2. We haven't decided yet whether to put in a real furnace ($$$) or maybe a catalytic heater (are those safe?) so couldn't I just wire nut off the black and white (separately, of course) and have it there when/if I need it later?Catalytic heaters are safe, as long as you remember to have a window cracked open to provide fresh air. They will consume the oxygen in the trailer if the trailer is totally sealed up. In the fight for oxygen, the heater will win (not good for other things that need to breathe).
3. The wire in the cabinet at the front of the trailer (11.6 reading) isn't needed for anything since there are already enough lights there so could I somehow bring that wire down through a wire chase and around the perimeter (all the way around) over to the fridge and use that as my maybe-I'll-need-it fridge wire? Just have it hang out there until I need it?Sounds good to me. Use the same gauge wire it is now to add the extension. Run both the black and white wires so you have a complete circuit.
4. Can I run a 14 gauge wire from the connected wires in the closet to power a reading lamp over the bed? Yes
If I put the 14 gauge wire in with the black wires, how do I ground the light? Put the ground wire in with the white wires in the wire nut? Iíd extend both the black and white wires from the closet to where you want your lamp and use the white wire as the ground/return.
5. Finally, a bit off topic, there is a little tube sticking down in the back with a little threaded hole above it to the outside. The PO said this was a vent tube for the battery but when I blew on it I couldn't get any air to go through it. Any idea what this might be? You put your mouth on it and blew into it??????? Brave lass you are! No idea what it might for though. Looks more like a drain than a vent.