Once passed through, connect the male plug to the original female headlight plug-in this case, on the passenger side of the car. This is the secret to making the system work and negates any rewiring. When the new harness is plugged into the old one, it relegates the old harness to handling low currents. The current now going through the old wiring only controls the relays, which-along with the new wiring-handle the current of the high-powered headlights. The unused original headlight plug is tucked away behind the headlight bucket.