the horn on my 68 f100 has not worked, i picked this truck up in november and now it's time to focus on the horn, with my schematic in hand i have tracked down the problem to the steering wheel, the blue and yellow wire coming from the relay comes into and attaches to the bottom of the plastic cylinder that the contract brush slides into, i can make the horn blow by taking my light tester touch the b and y wire end where it attaches to the plastic cylinder and poke it into the plate behind, horn works great, inspecting the contact brush it looks just fine, now if slide the contact brush back into sleeve clip on to the end of the contact brush and poke the plate behind nothing, now i've been working on this for a bit and am about cross eyed but would i be correct to assume the blue and yellow wire coming into the back of the sleeve has no connection to the metal connector at the base of the sleeve for contact brush to connect to? that can't be because i jambed a wire in the sleeve and ran it to the ground to the battery and horn worked???? knowing that i can ground b and y wire to plate behind and make the horn work it shows steering column is grounded properly correct?

thanks
dave

 

found the prob, what may look like a good working contact brush was not

dave

 

You'll find those type of grounding problems are all over these old trucks!!

 

thanks for your feedback, i work on this one so long i needed to step back from it, turned out to be simple and i made it difficult

thanks
dave

 

What was problem?

 

I just fixed mine and had to refresh the copper contacts and the metal on the bottom of the horn button with a red scotch brite pad. Works like a champ now, did take me about 4 hours of testing to figure it out.

 

Horn brush contains a coil spring with a tiny copper wire inside it. The wire snaps, the horn no longer blows.

 

"Wipers don't work, and the horn won't blow, but there ain't nothin wrong with the radio."

 

at least our trucks are not like some of that british stuff. you go to honk the horn and the wipers work.

 

My horn was working intermittently. I sanded the contact points on the horn brush and the steering wheel and put a copper BB under the brush, and replaced the ground strap on the rag joint. I tried a different horn.
then I discovered this little guy near the starter solenoid.


​​​​It's the horn relay, as you can see it was pretty corroded. Replaced it with a clean salvaged one and all is well.
I may end up rerouting it through a Bosch relay as I have extra room in the box I installed for my headlights, just to clean up the engine bay a tiny bit more.

 

I would suggest using a 30 amp Bosch relay. Especially if you have dual horns.

 

They get a little tarnished I noticed, the horn on my slick sometimes needed a couple tries to sound off, so I tried the easiest thing first and dressed it on some emery paper. Works like a champ now.

 

I think hooking up dual horns was the thing that finally pushed that old relay over the edge.
I'm back down to one for now...I found an old 6 volt VW horn in my parts stash the other day and would like to hook that one up as well though. It would scream as long as it didn't burn out.
I thought about mounting the horns closer to the road too, like the old VWs, to project the sound out more rather than into the engine bay. Or, at least pointing the open end of the horn out through a hole in the rad support.

 

German engineering is tops but you'd be asking a bunch of that horn. Try hooking it up with an in line 6 ohm resistor. I wouldn't point the horns forward. They would act like a scoop for rain, road dust, stones, etc.