Horn not working 2002f250 - 2002 Ford F250 Super Duty SuperCab

Disconnect the horn wiring at the horn. Check for voltage at the horn when the horn 'button' is pushed. If there is voltage at the horn, the problem is the horn has died. Remove and replace. No voltage at the horn is most likely related to the horn 'button' but could be wiring. Could also be corroded connections at the horn wiring.
Just had to replace the horn on a 2011 Chevy.
A 1930 Model A horn still works though.

The horn relay primary receives + full time and is actuated by receiving ground (-) from the horn button. Check ground continuity at the horn button (at the steering wheel) to make sure it is working first (most likely culprit). If the horn button is working, check to see if the horn relay is working (second most likely culprit). To test the horn relay, provide chassis or battery ground to the (-) primary terminal of the horn relay and see if the horn honks. If it does, that will tell you that the problem is in the wiring between the steering wheel and the relay, most likely a disconnected wire at the steering column.
The only other components in the system are the fuse for the horn circuit (if you have 12v at the horn relay, that is fine), and the horn itself. My bet is on the horn button pad itself.

Inside of driver fender up by door

WITH KEY ON EVERY THING ELSE OFF PUSH THE HORN YOU SHOULD HEAR A SMALL CLICK THAT THE HORN RELAY IF SO TEST FOR POWER AT THE HORN MAKE SURE IT IS STILL CONNECTED IF POWER IS GOOD REPLACED HORN

If it is not running hot it could be low on coolant or have a bad sending unit or sensor

There will only be one fuse for the horn. Find and check the horn relay. If that works check the wiring and the horn switch..

Could be bad horn or relay or the horn'button'.Start at the horn with a test light.Have someone push horn button and check for power at the horn.If no power then trace wires to relay,check for power cominginto relay.If power is going in but not out to horn relay is problem.etc. Some horns have a lttle knob you can turn to adjust them and get them working

Im in the same boat with my 99 civic si. it is wiring in the steering wheel that is causing your horn to not work. it is a lot of work to replace the wire in the steering wheel, so if you want a horn, my suggestion is to wire the horn to a aftermarket switch. it is a cheap and easy solution and will get the job done.

Maybe horn became unplugged. Put 12 v power to horn make sure horn works. Put test light on terminal on horn have someone press the horn button, if light comes on and horn does not blow you may need new horn. if light does not come on you may have bad contact at horn button, blown fuse, broken wire, bad horn relay or possibly just a bad ground.

Unplug the wire to the horn and make sure you have the horn grounded really good. Take a hot wire and run it from the battery to the horn. touch the hot wire to the end of the horn and see if it works. If it does not work then you need to replace the horn. If the horn works then take a test light and hook it up to the horn wire and have someone push the horn down. you should have a hot wire. If you don't them check the horn fuse. Let me know if this works.