Trailer Wiring Harness Installation - 2004 Ford F-150 Mar 14, 2013How to Install a Trailer Wiring Harness on a 2004 Ford F-150. All right. Today on this 2004 Ford F150 were going to install part number 118247. First thing we need to do is go ahead and unload our spare tire and get it out of our way.4.5/5(46)Category: Custom Fit Vehicle WiringBrand: Tekonsha 2004 ford f150 trailer wiring harness | eBay www›Search›2004 ford f150 trailer wiring harnessFind great deals on eBay for 2004 ford f150 trailer wiring harness. Shop with confidence.