Horn Sound

[Dollar Bill]

I get the aahoo but no gah.

Car is 12 volts and the fields appear to have been rewound as the windings do not lay neatly beside each other as you would expect and there is no step down resistor.

Everything is clean and lubricated. Didn't want to fiddle with adjusting screw for fear of making it worse without confirmation from the horn pros.

[Tom Wesenberg]

Fiddle with the screw. You can't hurt anything, and it only takes a click or two in either direction to make a big difference. If you have a 6 volt horn running on 12 volts, then you may never get the correct sound.

To lower 12 volts to 6 for the horn, you could try a 1 ohm 50 watt resistor.

[MikeK]

There is a tension leaf spring that keeps the motor shaft axial play biased rearward, separating the ratchet and diaphragm pawl. THREE things must be correct to get the correct ...gaa at the wind-down: 1) The backward shaft end play controlled by the 'adjust' screw. 2) Maximum forward end play, fixed by spacer washers as needed on the front end of the motor shaft. 3) Tension of the leaf spring that pushes the armature shaft backward, away from the diaphram. This is Bratton's picture of it:


I suggest you look at both the armature forward end play, which needs to be present to the correct amount, and the tension spring, which must also be set correctly. I assume you have the diaphragm oriented correctly, following the tiny position locator hole and frame detent.

The motor armature is/should be offset from the magnetic center of the field coils toward the rear, away from the diaphragm. When the motor is powered the armature moves forward magnetically, overcoming the force of the spring shown. That spring is a point of question if it is replaced. Most of the replacements I've seen are way to thick/stiff compared to originals. The rear 'adjust' screw only finds the horn work point. That not-too-easily accessed and almost never adjusted front spring has a major influence on the overall voice. I've made a few of those springs from steel strapping and they worked way better than the too-stiff aftermarket replacements. Whatever you have, if there is no wind down -gaa that spring likely has too much tension. Bend it to adjust.

The visual center and the magnetic center are not necessarily exactly the same. If a motor is running with no shaft end play limits or forces the armature will find the exact magnetic center. Repair/rewinding any part will slightly move that point. The horn must have the forward end play set so this magnetic center point is NEVER reached. The armature must be rearward so any application of power will tend to drive it forward. An improper set of shaft spacers/washers will cause this.

The forward end play limit is set by the contact of the diaphragm pawl to the ratchet wheel. During manufacture, with all identical parts moving down the line this point was fixed by the height of the U shaped field frame. Now, with tolerances out the window with replacement and swapped parts, some people adjust by peening around the diaphragm pawl to move it in/out, by changing diaphragm shim thicknesses, or by stoning the ratchet and pawl to modify the engagement.

Unfortunately I've encountered too many finicky or 'sick' horns from rebuilders and rewinders who did otherwise good work. Attention to the above puts them in good ahoo-gahha voice. In many cases just a change in the diaphram gasket thickness when it is replaced throws the horn into an unwanted wind-down tune.

[burner31]

Play with the screw, you wont hurt it

[Dollar Bill]

Thanks guys, I will play with it today after of the neighbors are awake. Will let you know the outcome.

Mike that is a comprehensive and very informative reply. I now better understand the finer details for the origin in the missing gaa from the horn. If fiddling with the adjusting screw doesn’t produce the proper note, I now feel more prepared for further troubleshooting.

[bobpo1]

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Having had Ahoogah horns powered by both 6 and 12 volt, the difference is with the 6 volt the sound is AaaOoooGaah. The 12 volt sound is Aaoogah, much faster. I like the 6 volt sound better.

[Ray in La Mesa]

I keep my neighbors happy when adjusting the horn by wrapping the bell in a fluffy towel & a bit of tape. You can hear the AHOOGA clearly but quietly. Only when I am satisfied with the AHOOGA do I pull the towel off.

[monto]

Thank you all: very enlightening...