Horn Quandary


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Oct 8, 2019
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My Car
1971 Mustang Convertible
1971 Mustang Mach I
1972 Mexican GT-351
This applies to the Mexican GT-351 i just got.  I did some troubleshooting on the horn. Note these are Mexican made horns and a bit different that ours

1. The rim blow wheel is in constant contact.  I measured resistance across the two wire leads as 2.1 ohms BUT the horn does not "work" in that it should be blowing the entire time (which it doesn't).  Both wheel connectors are at 12v to ground with the wires connected to the pins,

2. SO the horns....i took both off and cleaned up the interface locations to make sure there is a good ground.  I bench tested both and they both work.  I reinstalled and was only able to check one horn while installed for correct function.  It worked fine.  The connector on the other is not at all easy to get to with the horn installed so i am assuming it is ok.

3.  The schematics SUCK that i have been able to find. I only have 71 Mustang schematics (there is no horn on my material that i could find).   A friend has the electrical schematics course material that Ford used.  For Mustangs it is no better.  We pieced together what MIGHT be applicable from some of the other vehicles schematics.

4.  I plan to check continuity from wheel to horn connector next but i imagine that is broken otherwise it should work. Right?  I will then check continuity at the connector on  the bottom of the steering column (wheel to connector and connector to horn).

5. Any suggestions?

My next question is going to be on brake lights but including here since it may be of interest.  The driving lights all work as do the turn signals.  I have not checked the reverse lights yet.  Any help from the collective group would be greatly appreciated.



Shorts checker
Jan 24, 2012
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Tucson, AZ
My Car
No Mustangs at the moment.
Horn wire connectors are notorious for corrosion and bad resistance.  About 50% of the time I have to remove the cover and clean and re-crimp the horn connectors in the engine compartment.

Hope this helps.