I'm trying to figure out the wiring in the coach battery compartment of a 86 Sunrader. When I bought it, it didn't have a coach battery installed. I just bought a deep cycle RV battery, There's 5 wires with ring connectors, 3 white and 2 black in the coach battery compartment. So far, I've determined that one white is ground, because it bolts to the chassis on the other side of the propane tank. 2 black are positive. 1 black wire is reading 7 vdc when I touch ground with the other lead of my meter. So, I know that connects to the positive terminal of the coach battery.(Obviously, at the manufacturer, they didn't care which color wires they used for positive and negative.) The other black wires goes up to the isolator on the firewall under the hood. It's a two connection isolator, a red wire coming off the other side of the isolator has been cut and went to nothing. I connected it to keyed power, so I know that has to go to the positive post on the coach battery. As for the other two white wires, one has +12vdc when 110 AC is plugged into the converter when I measure it on my vom, with the other terminal of the meter touching ground. So I know that white wire goes to the positive side of the coach battery. I tried to follow the other and last white wire, and I've lost it up on top of the gas tank in the harness. There's another two connection plug coming out of the harness up near the top of the gas tank that's plugged in to nothing. I've recently installed a new gas tank and new fuel pump inside of the gas tank. When I had the gas tank down and doing that work, I know the fuel pump is wired up correctly, and that plug didn't go to that fuel pump at all. I'm thinking maybe the back water pump near the water tanks to pump water to the shower and the sinks etc. Is where that wire is supposed to plug into coming out of the harness, but neither of the two wires coming out of the harness with that plug on it are white. I can't find any other plug anywhere down there where that plug might plug into. So I've lost the white wire coming out of the coach battery compartment into the harness up near the gas tank. It doesn't have any continuity to ground, so I'm guessing it has to go to the positive terminal of the coach battery. I just want to be 100% sure when I hook the coach battery up to all of the 5 wires. So if my assumptions are correct, there would be five wires in total, four going to the positive terminal, and one going to the ground terminal of the coach battery. So my question is, does anybody know where that other white wire going into the harness by the gas tank goes to? And where is the water tank water pump? How is it wired? And where that mystery plug up near the top of the gas tank coming out of the harness goes to? And am I correct, two black wires two white wires going to positive terminal on Coach battery? And one ground white wire to the negative terminal on the coach battery? Any help would be greatly appreciated.