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FAQ - General Installation Instructions for Heavy Duty Headlight Wiring Harness
General Installation Instructions for Heavy Duty Headlight Wiring Harness
  1. Unravel wire harness and lay out in your engine bay (Caution! engine may be hot!) to make sure there is sufficient length.
  2. connect the 2 power wires (fusible links can be black, red or green to red wires on relay socket*) to the positive (+) terminal on the battery. Tip: you can temporarily disconnect the fusible links to the rest of the wire harness for easier install.
  3. Unplug the factory headlight socket(s) on the side closest to the battery,
    (i.e. if your battery is located closer to the driver side unplug the headlight socket on that side.) and plug into the mating socket (socket that resembles the back of a headlight bulb).
  4. Plug the new wire harness headlight socket into the bulb and attach the ground wire to a major metal section of your vehicle (you may ground to the battery negative terminal if possible). Be sure that your ground is to something that is rust and paint/undercoating free, it must also use a screw that conducts well. (note: most of the problems occurs with improper grounding.)
  5. Do the same with the other side.
  6. Plug in both relays (one is for low beam, the other for high beams) and apply electrical contact grease (or similar) to prevent corrosion.
  7. Turn on your headlights.
*note: fusible links function as a slow reacting fuse and provide more power
NOTE: for vehicles with dual batteries (such as the Ford Super Duty) it is recommended that 2 wire harnesses be used connected to each battery.