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I am trying to figure out which wire goes were being as the original horn was removed, both of the two coming off of the box next to the horn are yellow so its impossible to tell which is positive and which is negative. I have tried to use my multi meter but I don't see how i'd find the hot lead without pressing the horn button =/
The horn button provides the ground path to the relay. Basically, you have power coming in to the relay and being split out to both the horn button and the horn. The wire to the horn button first goes through the magnet coil in the relay, and when you press the button completing that circuit, it closes the contact sending power out to the horn.
You should have power on one wire at all times, one with continuity to the horn (or about 4ohms resistance), and the other open until the horn button is pressed.
OP has a 1972 F100: 1971/72's have a two spoke steering wheel and a vinyl horn pad. 1967/70's have a 3 spoke steering wheel with either a horn ring (Custom Cab/Ranger) or horn button (Standard Cab).
There is no separate horn wire on trucks of this vintage unless it's a P Series Parcel Delivery. The horn works via the turn signal switch with a horn ring, horn button or vinyl horn pad.
The steering wheel was out of a 1960s I installed a grant wheel I am able to get it to respond now when I hit the button but it just makes a clicking sound. I was able to find the constant and it isn't constant it goes up and down and has only hit about 2.9 ohms. Could the box mounted to the radiator support siimply be bad? I hooked it up to the ****** and theres nothing wrong with the horn itself.
My turn signals still work just fine plus I only felt like spending $50 on a replacement steering wheel. The horn works but its hit or miss sometimes the air horn goes off sometimes it just makes a clicking sound. I don't think its getting enough juice that or it isn't grounding out right. The ****** has the horn wired directly to a botton and it blows your ears out everytime you hit it so I know the horn is good. I'm just gonna hot wire the horn and be done with it. The 1960s f250 that first wheel came off has been in the family since new, my grandpa let us put power steering in it in 2009 so I wasn't sure if it was original or not and wasn't surprised when it started turning my hands black and the rubber finally gave out.
On another note I got it to work everytime I scrapped off the paint where the horn button makes contact with the horn.