I purchased so multimeter leads to help test for things like this.
https://www.amazon.com/gp/product/B08PBHX3QM
I also made a 20’ alligator clip to help with continuity over long distances.
Of course you should trace the wire back as best as you can, but I found my wires all over the place when I peaked in my RV underbelly, so that is a hard job and at some point I’d bypass finding the exact break and runs new run for what is not working.
Another thing I found in removing panels to get access is there is a double square bit which seems to be unique to the RV industry, and I found a single square did not work for me.
https://www.amazon.com/gp/product/B08LNYQQ4P
I am far from the bast at removing paneling but I was able to get most of the nailed paneling to gain access to pipes with just a screwdriver, but there has got to be a better tool for it. Sometimes the backing was not thick enough to replace the panel and I was able to glue a thin sheet of wood behind it and the screw held better.
I have a snake camera to look at places that are hard to get to, but this never gets the view I want.
I have the bullet driven nails that hold the chloroplast on. I Don’t recommend drilling the screws out. I Recommend getting a cats claw and tapping it with a hammer and then prying the nails out. If that doesn’t work, I Drill out the nails, but it is a huge pain and much easier to pry the nails out. I do replace the nails with screws.
The RV underbelly tape
https://www.amazon.com/gp/product/B09HJVTLSJ
is pretty awful at staying on, even with good surface prep and cleaning. Where I cut into the underbelly, it is peeling off on the windward side of the underbelly. When my camping season starts, I have a black gorilla tape to try and it can’t be any worst than the RV underbelly tape.
Be careful with the underbelly chloroplast. This is not a cheap thing to replace. I looked up the price to replace mine and it was hundreds of dollars just to purchase the chloroplast underbelly for my RV. The screws and washers hold it securely. I have a 3’ section of tape.
I have a PEX crimped for any of the piping jobs that need to be replaced.