Intermittent Working Horn

[spdway1]

85% of the time, my horn does not work. What fun is that?
It will work intermittently when I spin the horn button while pressing it. Do you think the ground under the horn button needs cleaning, or is a problem elsewhere?
Note: It has a brand-new wire harness, and the horn is strong when it works (lubricated properly and clean).

How do I go about fixing it?

(1930 Unrestored AA Grain Truck)

Thank you for your help and time.

[Marshall V. Daut]

Yes. That you have to twist the button to make the horn honk is the classic symptom for rusted or corroded contacts beneath the button. You'll have to remove the light switch rod from the steering column, which can be problematic if you have a coupe. It can be done in a sedan without removing the steering column by slightly bending the rod as it exits the shaft. Kinda tricky, but it can be done. Once the switch rod is out of the steering column, you can pry the tangs up to disassemble the underside of the switch head and sand the contacts. Reassemble and bend the tangs back over. Slightly bend the rod and shove it down the steering shaft.
Marshall

[ronn]

sell it and buy another- easy fix.

[nkaminar]

My advice is to not slightly bend the rod as it may put a permanent bend in it and cause it to turn the light switch when turning the steering wheel. Instead, remove the bolts that attach the steering box to the frame and the bracket that holds the steering column and tilt the steering column down. You will have to take off the light switch at the bottom of the steering box and remove the keeper and spring that holds the rod and the spider that turns the light switch.

If you decide to clean up the old horn switch and not buy a new one, after getting to bright shinny metal, but a thin coat of electrical grease on the metal parts to keep them from corroding in the future.

[Marshall V. Daut]

Yes. Lowering the steering column will help some. I should have mentioned that. Good catch.
M.

[JayJay]

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I had that same issue. Turned out that the horn was just exquisitely sensitive to the adjustment screw. I backed it off, heard the motor spinning freely, then screwed it in one click at a time until I got the proper ah-hooga. That adjustment turned out to be one click out from where I had been running it (with intermittent non-response) for years. No issues now six months later, still a good strong ah-hooga. One down, now probably at least 38 to go (but who is counting).

Don’t forget that there are two little felt pieces, one at each end of the commutator, that need a drop of light oil one in a while. They lube the shaft.

Never hurts to clean the commutator with some cleaner, and maybe a light burnishing with fine grit paper. I’ve also had the little brass strips behind the brushes that push the brushes tight to the commutator fail - probably aftermarket crap from years ago.

Also, if all else fails, consider cutting in a relay so that the motor amperage isn’t going through your horn rod. I have not had to do that on my present car but did on another one I sold. Agreed that you should not need to do this but it’s an option.

I’m not sure that even lowering the column will give you enough room in a truck cab to get the light switch rod out. Truck cabs are pretty tight. You will need at least 46-1/2” from the steering wheel straight back to the cab to get it out. If you go that way you may need to pull the whole column and steering box out, or at least remove it and move it forward (at which point you may as well pull it out completely). NK is correct, once you bend that rod (which is really easy to do) you’re in for a host of trouble.

[katy]

you can pry the tangs up to disassemble the underside of the switch head and sand the contacts. Reassemble and bend the tangs back over.

I've done that and 2 of the tangs broke off. The "cage" that holds the button is not available as a separate piece, so I soldered it back back in place.

[JayJay]

Originally Posted by katy

I've done that and 2 of the tangs broke off. The "cage" that holds the button is not available as a separate piece, so I soldered it back back in place.

Very small tip on your oxy-fuel torch, soften the tangs so they bend easily. Repeat to reassemble.

[Jim16A1]

Once I removed my horn rod, I was worried about breaking my tabs, so I sprayed a bunch of Deoxit D5 underneath my horn button, then worked it around by pressing the button in and turning it a bunch. Checking resistance with a multimeter while moving the button will help you find any “dead spots” in the button. Don’t forget to clean off the end that goes into the wiring hub as well. This made a night and day difference with my horn.

[katy]

Very small tip on your oxy-fuel torch

Not everyone has one of those.

[Fullraceflathead]

They make a very small handheld butane torch that I believe is available at harbor freight I think they're under 20 bucks.

[nkaminar]

Jay Jay, Post #6, has a good tip. I do that myself from time to time. The horn needs occasional adjustment.