[rickst29]

(1) These wires are dual 12V grounding wires, even though the color is not white. They go through the floor and get clamped to the frame within in a small, black plastic "cover box" behind the sewer drain assembly. Up at the batteries, the WHITE battery ground wires end at a clamp into the frame. The frame is the 12V "Grounding Wire" among those 3 clamps. You might want to verify that all of those clamps are clean and very tight - your TM has a lot of years, and probably a lot of miles, to loosen the clamps and corrode the connections. You might also want to increase the wire size.

(2) With one wire disconnected, you are currently running off the battery OR the converter. You need both wires connected. The WFCO board designated "Main" connectors for the purpose of supporting large wire sizes in the clamps. If your new board can connect #8 "downstream" from any fuse, choose one of them for your new #8 wire, and put in a 40A fuse. (If your Converter is bigger than 40A, then you need a bigger fuse - even though the wire size is typically quite small.)

(3) For 12V DC connections, Bus Bar == Terminal Block, you did fine. Just make sure that the Terminal Block is connected to both of the "Grounding Wires" going to the frame (the wires in question 1).