Some thoughts may work for finding this wire but it is also good to keep in mind that not all the same year, make, modle will have the same options, so that can leave the wiring harness having some spare leads if that specific Rv doesn't have a specific option!
So one way to go is to look on the wire side for a code. check the first snip below for example? Then if you find a code, check this link for wire ID as it may give a good idea of where that wire is "from" and "to":
https://www.winnebago.com/Files/File...ical_guide.pdf
If you don't have that item, then it is just a spare wire!
Second way might be to use the drawings and start at some known point to test for voltage there and work toward where you want it to go.
A good point to start is often getting the battery charged and then working from there toward some item like lights of a fan that is easy to find and check.
Maybe try looking for the loose wire ID and get back with some info one what else you have to work with. Do you have a meter or way to check wiring for voltage? Do you now have the battery charged?
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Richard
Why no RV year, make and floorplan on MY signature as we suggest for others?
I currently DO NOT have one!