Horn Relay wire question - ClassicBroncos Forums Horn Relay wire question Bronco Tech Community Message Forum Photo Gallery Event Calendar Book Reviews Bronco I've been through many of the horn relay posts but was unable to find an answer to my wiring question. I have the horn relay. Either someone with an actual Ford 3-wire plug, Early Bronco Alternator Gauge Installation in Centech Click to view on Bing2:26https://wwwbroncoparts/produ.. How to install an Alternator Gauge in your 66-77 Ford Bronco with Centech Wiring Harness.Author: Toms Bronco PartsViews: 3 Horn Question - ClassicBroncos Forums Have a '72 Bronco. Trying to install new horn. Have only had the truck for about a month now and know very little about electrical systems but have been told that the wiring is new on the truck. This seems to be true as all the wiring looks practically new.