The black wire from the smoke unit does not need to be attached to the reverse unit. Regarding the smoke unit: one wire should be grounded to the frame, usually the screw that holds the cross head guide to the shell. The black wire can be attached to the center rail pickup. There is usually a wire that goes from the pickup to the reverse unit. Further, usually 3 wires are wire nutted together 1) the center rail pickup, 2) a wire from the reverse unit, 3) the wire from the smoke unit. There is nothing on the reverse unit that controls the smoke unit. Some loks had a smoke unit on/off switch. Lionel did away with it as a cost saving measure.
Steve
