I am wiring my expansible van to be powered by external 115VAC household current via extension cords. According to the electrical schematic on the door, the 8 ceiling lights are each wired with 3 wires. They appear to be labeled on the schematic as 650, GRD-N and GRN-C. I am not an electrician. Can you tell me which wires from the 115VAC supply I connect to the 3 light wires mentioned and if those are correct? Thank you very much!