Got some GM style horns for the 4runner, mine was missing all together. Problem was that the wiring to the horn button on the steering wheel of the Toyota are hot all the time & switch on the ground, but the GM horn ground to the chassis thru the mounting stud. The solution was a 20 amp relay. Full time hot (from original horn wiring) on 87 & 86 on the relay, gronund from original horn wiring to 85 & 30 to the horn positve. Easy deal & works great.
Rob I, working on getting my horns wired up. Problem is my OEM horn wiring is shit. I have the relay needed. Kinda lost on what I need to do. Im running a new wire from the horn button into the engine bay but kinda dont know where to go from there. This type of stuff isnt my specialty