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Old 10-07-2020, 10:07 AM   #1
fordmerc7
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Default horn blows while driving

Horn on my '29 sounds intermittently while driving; Sometimes a lot, sometimes just a bit of sound. Recent onset of problem. How should I troubleshoot this? -or is this a common problem with an obvious answer that I missed?
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Old 10-07-2020, 10:37 AM   #2
Robert/Texas
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Default Re: horn blows while driving

When mine did that it turned out to be that the c-clip/keeper had worked itself out of the light switch spider.
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Old 10-07-2020, 11:47 AM   #3
jg61hawk
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Default Re: horn blows while driving

Mine starting low "growl" as I was driving. I found if I hit the horn button it stopped for a while. That made me think it was not in the wires. I eventually got it to growl while sitting still and I found the screw on the cover (not the adjuster screw the hold the cover screw) apparently was too tight. As I loosened the screw the growling stopped and never returned. Just a thought: Try driving with the cover off if you want.
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Old 10-07-2020, 01:58 PM   #4
duke36
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Default Re: horn blows while driving

Check the spring and spider clip as suggested in post 2.. Also, check the copper bushing at the top of the horn rod so it and the rod seats properly so as not to ground below at the switch housing when turning the wheel or going over bumps...
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Old 10-07-2020, 07:27 PM   #5
Jacksonlll
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Default Re: horn blows while driving

If everything looks good, it might be that the tip of the horn rod is grounding against some metal. I have fixed a few using a large soda straw, plastic. Cut a small piece and slip it over the end of the rod. Good luck.
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Old 10-07-2020, 07:58 PM   #6
J Franklin
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Default Re: horn blows while driving

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Maybe your car was used in too many parades and took a set!
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Old 10-07-2020, 08:28 PM   #7
Pat/Ohio
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Default Re: horn blows while driving

When I installed a new wiring harness and light switch cover, my horn would sound when I connected the battery. After doing some research on the new light switch covers (repro) I discovered that my light switch cover wasn't mated correctly and the end of the horn rod was resting against the metal in the cover. I ground a little of the bottom cover off (as instructed by Brattons) and was able to securely and evenly install the bottom half of the cover which placed the horn rod in the center of the switch. Problem went away.

Good Luck,
Pat
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Old 10-08-2020, 07:53 AM   #8
Ray64
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Default Re: horn blows while driving

My horn wire on the light switch was half broken and the loose wires were shorting on other wires
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Old 10-08-2020, 03:10 PM   #9
fordmerc7
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Default Re: horn blows while driving

OK, lots to check out. Unable to work at it in past few days but this weekend will be for troubleshooting.
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Old 10-09-2020, 07:39 AM   #10
old31
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Default Re: horn blows while driving

Quote:
Originally Posted by Jacksonlll View Post
If everything looks good, it might be that the tip of the horn rod is grounding against some metal. I have fixed a few using a large soda straw, plastic. Cut a small piece and slip it over the end of the rod. Good luck.
Well, aren't you clever Mr. Macgyver.
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Old 10-09-2020, 01:18 PM   #11
J Franklin
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Default Re: horn blows while driving

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Originally Posted by Jacksonlll View Post
If everything looks good, it might be that the tip of the horn rod is grounding against some metal. I have fixed a few using a large soda straw, plastic. Cut a small piece and slip it over the end of the rod. Good luck.
Maybe use some heat shrink tube, a straw seems fairly thin.
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Old 10-11-2020, 07:53 PM   #12
30Ford
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Default Re: horn blows while driving

Horn grounding out on the mounting bracket
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Old 10-13-2020, 05:37 PM   #13
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Default Re: horn blows while driving

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Originally Posted by jg61hawk View Post
Mine starting low "growl" as I was driving. I found if I hit the horn button it stopped for a while. That made me think it was not in the wires. I eventually got it to growl while sitting still and I found the screw on the cover (not the adjuster screw the hold the cover screw) apparently was too tight. As I loosened the screw the growling stopped and never returned. Just a thought: Try driving with the cover off if you want.
I had a "growl" while driving as well. In addition, pressing the horn button resulted in what would charitably be termed "anemic" response that could not be adjusted out. Pretty embarrassing.

I disconnected the wires, checked continuity both on the 6 volt and ground sides and found all well. So I took the horn apart.

Found the cover held on quite tightly with the screw, one brush spring hypercompressed and non-functional, and the brush holders were missing the springs that hold them against the copper brush housing. The tension bar on the ratchet end of the armature had been replaced by what appeared to be a bent six-penny nail. And it was really dirty. Magnets and armature tested good.

So I gave it a thorough going-over. Once cleaned up, commutator polished and undercut, and brushes, brush holders, tensioner and wire ends (I replaced the grossly deformed crimp-on "bullets" with solid copper solder-on) replaced, it now gives a truly regulation "ah-ooo-gah" and no more growl. I have not tried to reproduce the growl by tightening the cover screw but that could have been that issue.

BTW, I ordered new diaphragm gaskets from Snyder's, they came a maybe 0.080-0.100" diameter oversized and didn't fit (holes didn't line up). So I resurrected the originals.

Success! Gotta love 90-year old electrical...

JayJay
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