A wiring harness assembly includes a first flexible planar wire cable. The first flexible planar wire cable has a first plurality of separated conductors formed in a first insulating layer. The first insulating layer includes a first flat exterior surface. The first flat exterior surface defines first apertures that expose at least a portion the first plurality of separated conductors. The first apertures are sized, shaped, and arranged such that arranging a second flat exterior surface of a second flexible planar wire cable in contact with the first flat exterior surface enables an electrical connection between the first plurality of separated conductors and a second plurality of separated conductors formed in a second insulating layer of the second flexible planar wire cable.