The Baja Designs OnX6/S8/XL Upfitter Wiring Harness (640094) is a single-harness adapter for wiring Baja Designs LED lights to a vehicle's factory upfitter or aux switch circuit. The manufacturer describes it as designed for vehicles with factory up-fitter/uplifter switches, and says it simplifies installing its lights. It is listed for the OnX6, S8, and XL series. It is sold as a single harness with splice connectors and one three-pin light connection. Owners on user forums often describe this kind of harness as the cleaner alternative to improvising a relay setup from a generic light harness, which can save guesswork on the wire colors and the switch-side routing. Searches for an OnX6 aux switch harness, an S8 upfitter pigtail, or Baja Designs factory switch wiring usually point to this part.
Fitment is the first thing to confirm. The manufacturer lists the harness as universal, and it is tied to the factory upfitter circuit rather than a specific model. Published fitment details vary, so check with the manufacturer before ordering for a particular Ford, Raptor, or Super Duty. The harness does not include a switch or mounting hardware, so it assumes you already have a factory upfitter switch or another control source. Owners on user forums report that the supplied wire ends can be short at the switch, so plan your routing before cutting anything.
No. The manufacturer lists the harness as including the upfitter harness only, with no switch and no mounting hardware. You will need to supply your own factory upfitter switch or other control source.
The manufacturer lists it as universal for vehicles with factory upfitter/uplifter switches. Published fitment details vary across sources, so confirm vehicle compatibility with the manufacturer before ordering.
Owners on user forums report that the white wire is connected to the upfitter circuit and the black wire goes to ground. Some owners also cut the supplied harness and splice it into the upfitter leads instead of using it as a plug-in piece.
Owners on user forums describe this as a moderate DIY job rather than a plug-and-play one. The main challenges are tight working space near the fuse box and upfitter switch area, short wire leads at the switch end, and routing the harness so it does not interfere with other components. Forum members commonly crimp or solder the connections and seal them with heat shrink, so a crimper, solder, and a heat gun are worth having on hand. For ground, owners often recommend a solid chassis point or the battery terminal, with a secure, clean connection. Test the upfitter circuit with a multimeter or test light before connecting the lights.
