2001 F150 Supercrew Horn Question
 

We have a 2001 F150 with a dead horn. When we click the remote to lock/unlock we only hear what I think is the relay, but no horn sound. Same thing when we push on the horn on the steering wheel. The weird part is that the we don't feel any 'give' when we push on the airbag/horn combo in the center of the steering wheel?? What could cause that? Also found the 20 amp horn fuse blown under the hood. We replaced that and still have the same conditions.. Switched out the horn relay with a known good one - still no change. The wiring to the actual horn looked okay but we swapped it out with a horn unit with one from another Ford anyway- no difference. Now looking for my volt tester to check the wiring for voltage to the actual horn unit. Thought the membrane switch under the airbag might be bad, but if it was, then the relay wouldn't be clicking, or am I wrong about that? The airbag light is not flashing otherwise I would think it might be the clock-spring. Anything else I should check when I find my voltage tester?

Check for voltage at the hose fuse, check for voltage at the relay power pin, check for voltage at the horn when someone else is pushing the horn or if you have a panic button on a remote use that, check the resistance of the ground wire at the horn to battery ground, check the resistance of the power wire at the horn to battery ground.

Do you need wiring diagrams?

Thanks scott.butler4! If you have wiring diagrams they would be greatly appreciated!

Ok, first we go over system operation - Fuse #7 which is a 20 amp fuse in the battery junction box(under the hood) provides power to the horn relay, the repay pins 1 & 3 constantly have 12V, when the horn button is pushed a ground is provided to pin 2 of the horn relay thus energizing the field coil and closing the relay allowing voltage to go out pin 5 and to the horn.
Unfortunately this is a old vehicle and the online wiring does not provide connector face views nor location views so you will have to figure that out by following wires and using the wire colors in the diagram to figure out which wires are which.
We shall start with everything plugged in and the voltmeter tester on the battery ground terminal.
First make sure that there is 12V at fuse 7, then remove the horn relay and check there is 12V at pins 1 & 3 in the relay box for that relay.
Next with the horn relay still removed take a jumper wire and use it to jump pins 3 & 5 in the fuse box, this will simulate the horn relay being closed and the horn should sound.
If the horn sounds then you know that the wiring on the relay output and horn is good, thus the issue is the control side.
If the horn does not sound then you know that the wiring on the relay output and horn is bad and should be fixed before looking at the control side.
I would stop at this point and update us as to what happened for better further diag, if you would like to go further without waiting for more diag steps do what is below.
The if the horn sounds during the jumper wire test then you should reinstall the horn relay, find connector C234(most likely on the steering column) and disconnecting it, you would locate the pin for the dark blue(I believe thats what DB means) wire on the vehicle side of the harness and jump a ground to it, this will simulate the horn being pushed while removing the clockspring and horn switch from the diag.
https://cimg2.ibsrv.net/gimg/www.for...aab00bce2b.pnghttps://cimg3.ibsrv.net/gimg/www.for...e357d5804b.png

THANKS VERY MUCH!!!! This should help us a lot! I am a hobbled senior so I have asked my son to come over to help diagnose the problem. Getting to do something with my kids, now adults, is always a good/fun thing to do! By the way, on a related question, should there be some "give" when we push on the airbag/horn combo in the center of the steering wheel? On every other car we have when we push on the horn/airbag combo to toot the horn, it seems to go in or depress a little. There doesn't seem to be ANY movement or 'give' when we hit/push/ or press down on the horn/airbag unit in the center of the steering wheel. Thoughts?

Oh, before I forget, are there any fuses for the horn or relay located anywhere else, such as in the cab below the dash?

The airbag should move in a little when you push on in.
As the wiring diagram indicates the only fuse related to the horn is Fuse 7 in the battery junction box, this fuse only provides power to the horn relay which is also in the battery junction box.

Thanks. There doesn't appear to be much(if any) 'give' when we push on the horn/airbag combo unit in the center of the center of the steering wheel. Scratching my head as to why the fuse blew. Had to be either a short or too much voltage being pulled through it.

You originally found the fuse to be blown, then you replaced it with a new fuse, did the new fuse also blow?

I don't think so, but I'll check it again since it was getting dark out (when i checked it) and my eyes are pretty old. I will let you know

OK, got a chance to do a little troubleshooting with my son. We feel the relay 'click' whenever we hit the horn or hit the lock/unlock buttons on the key remote FOB. Didn't really need to but just to make sure, but we swapped it out with a known good relay & and still got the same results. Figured that means we're at least good from the steering wheel up to the relay/fuse box . Also checked all fuses & they are all good, including the 20 amp that was blown before, and that I already replaced, it's still good. Then got our little 12 volt test circuit tester, the kind with the little light inside the handle, and decided to test to the horn connector. My son got down under the truck an unhooked the connector to the horn. He said the two wire colors are red and black, coming from the fuse/relay box going to the horn connector. Figured black is ground so I put the one end of the circuit tester to (+) positive side of the truck battery and the other end into the black (-) side of the horn wire, and the light in the circuit tester came on. Then did the reverse by putting one end of the circuit tester on the (-) negative side of the truck battery, and put the other side to the (+) positive side of the truck horn wire & got nothing. NO light. So it would appear that the trouble is somewhere between the horn connector and the fuse/relay box. My son tried to trace back the wires and said he didn't see any breaks in the wire but he couldn't be sure. We tried to do some troubleshooting/testing at the relay location box with the relay out, but I wasn't sure what the actual pin numbers and locations are, so I can't be sure of what results we got. You wouldn't happen to have the Pin number designations so i can continue testing? My thinking now is the trouble is somewhere between the relay/fuse box and the horn. Thoughts?

There is a simple way to determine what and where the problem lies.

If you hear the relay working,that leaves only the wire from the relay to the horn(s). or the horns themselves.
If,,,,,,,, you connect your test light ground clip to a good ground, stick the pointed end of the light into the plug at the horn terminal , depress the horn pad, the test light should lite If it does the problem is with the horn(s). If it doesn't light there is a break in that wire from the horn relay down to the horn..
What we do is stick a rag into each horn, so you don't become a nuisance, or go deaf, you can use a piece of insulated wire to bring power from the battery positive terminal down to the tab on one of the horns , it should blow ! If not ,sometimes a rap or two will loosen up the vibrating plate inside the horn and it may start working. Just be very careful when bringing that wire to the horn that you do not touch any metal part of the vehicle ONLY THE TERMINAL ON THE HORN, or you could do some welding.
You will know if the horn is capable of working or not.
Many times the horns get exposed to moisture and road dirt and freeze up internally and sometimes the rap or two works.

Ok I crossed out everything with red that can be eliminated.
Remove the horn relay.
Check with a voltmeter that you have 12V at pin 3 of the relay(Orange arrow), just to make absolutely sure.
Jump 12V from the battery to pin 5 of the relay(Blue arrow), note if the horn blows or not.
Using a short piece of wire jump between relay pin 3 & 5(Green arrow), note if the horn blows or not.
Remove the horn itself and apply 12V to the red wire pin and a ground to the black wire pin, note if the horn blows or not.
Below you will find a picture of different types of relays and their pin numbers.

Are you aware of how to test the resistance of a wire?
https://cimg1.ibsrv.net/gimg/www.for...b5672bb7e4.jpg
https://cimg2.ibsrv.net/gimg/www.for...498b569205.png

Thanks again 'scott.butler4', and also to 'hanky' for all the help and advice. Gonna scrounge up a jumper wire to bypass the wire from the junction box to the horn itself. The information on the relay. shows me that we have the Basic 5 Pin Micro Relay, and now I know what pins are which so I can continue troubleshooting. I have to be honest, this troubleshooting might seem simple to other but its pretty fascinating to me. Of course, I have been cooped up inside since last March because of covid so doing anything outside that is meaningful is a treat. Anyway, I will keep you guys in the loop after doing my testing.

You can just use a paperclip as a jumper for where the green arrow goes.

Found a metal paperclip and jumped the 3 to 5 (connections after removing the relay). No horn noise after connecting the 3 & 5 with the jumper. My son has all my testing equipment in his car so when he comes over again I will ask him for help. I did manage to drop the relay somewhere in the truck engine compartment, when I pulled it out. Will ask my son to find that as well. In any event my guess right now is a broken positive wire somewhere from the horn to the junction box. I wonder if there is a way to run a new wire inside the wire loom to the bottom of the relay in the junction box down to the horn positive (+).??

By the way, do you know what florescent UV engine oil dye I can use that isn't the same yellow/green color used in the cooling system? I already put some of that in the coolant to check for any leaks and i want to do the same in the engine oil. I know there are leak detection kits that have different color florescent UV dyes for the different automotive fluids but I can't afford a kit. A very old neighbor, who is a long retired mechanic, said he knows there are UV dye colors like blue, red, & white, but he can't remember much more than that . I asked the girl who answered the phone at the local auto-zone about engine oil UV dye's and she said she didn't know of any color but the yellow/green. Thought i would ask here.

You are correct that it will be a broken wire between the relay output and the horn, I just like to 100% rule out everything else by checking with a voltmeter.
Yes you can run a new wire from the relay to the horn, its called a overlay.
The correct way is to cut open the harness, locate the correct wire, check resistance to find the open and then cut open the harness further along the correct way.
The issue with a overlay is that there may be other wire damage at that location that you would find if you actually locate the open.

No idea about the leak dye, only ever seen the bright green stuff.