35 Horn Problems

[jfcrash]

I am attempting to clean, and paint a pair of horns for my 35 Phaeton. They work fine on the bench, one a little louder than the other…they were never on this car.

I took them apart into three sections, the top electrical/motor section to which I need to solder two input wires, the middle flange section, which bolts up to the top section and the trumpet which attaches to the middle flange.

After some sanding and cleaning I bolted the top two sections together, applied 6V and no sound except for some humming…as I loosened the 6 screws holding the top two sections together, the horn sound came back to loud…. as I retightened the 6 screws I lost the sound again…

Anyone been down this road?? What did I screw up???

Thank you, Jim

 

[trainguy]

Then reason they hum is that the forgot the words.Try cleaning the contacts.Phil

 

[jrhaelig]

Would the fact that sound returns when the housing is loosened indicate that something is being pinched instead of being able to vibrate and make sound?

Although - at this point mine is loud as heck on the bench but only hums when installed. That sure indicates a loss of voltage, so that is probably your situation as well.

 

[FL&WVMIKE]

jfcrash .......................
Your horns will have a different tone. They were designed to harmonize. If the two sounded the same, you would have two "L" or two "R" horns.
MIKE

 

[TerryOH]

The wire end terminals to the horn slip under the two metal fingers and clip in place by the finger so no soldering is needed. All of the screws in the perimeter of the horn effect the sound and the adjustment of the horn. Assemble all the screws and mount the horn to the mounting bracket. Then if the horn needs adjustment loosen the small lock nut on top, slightly, and slowly turn the larger nut for Max. volume, all it takes is about 1/4 of a turn either way and then re-tighten the lock nut. You may have to redo the adjustment after the lock nut is tightened, since a very small change makes a big difference. The horn set comes with two different tones but the tone is derived from the thickness of the diaphragm and the size of the resonator cup under the diaphragm, not the adjustment.

 

[richard crow]

TERRY OH got it right

 

[jfcrash]

Thanks Terry,
I will try as you suggest over the weekend...
With the diaphragm being tightened between the top plate and the middle flange, what resonates to make the sound? Does the hex bolt shown in pic #2 come into play ??


Thanks Jim

 

[TerryOH]

The thin metal diaphragm vibrates causing the sound. Look at the horn assembly as an electrical solenoid. When the solenoid coil is energized the center pole piece moves. There are electrical contacts on the pole piece that open and close, along with the diaphragm that also moves with the pole piece. When the contacts are closed the solenoid coil can be energized, when they open the solenoid de-energizes. This happens very quickly and the pole piece moves back and forth causing the diaphragm to move back and forth along with it. This movement of the diaphragm causes the air to move and results in an audible tone. The faster the movement the higher the tone. So for the horn to even work the electrical contacts have to be closed without power on the horn and when the pole piece moves the contacts have to open. You can depress the pole piece with your hand to see this happen. The adjustment nuts allow this to happen at the exact moment when movement is the greatest and thus the sound output the loudest.

 

[jfcrash]

Terry,
Completely reassembled both horn assemblies with all screws, mtg brackets and cover. One worked fine, the other required adjusting the large nut per your guidance...both seemed to draw 3 + amps.

I was able to push on the hex nut on the bottom of each diaphragm and observe the points breaking as you mentioned....seems like one required more force than the other to see the movement.

Feeling good about these mechanics, I will take them apart again and make ready for painting....does that pole piece require any lubrication ??

Thanks again and to others,

Jim

 

[TerryOH]

no lube on the pole piece.

 

[flatheadfan]

JF-

Lots of good suggestions here. Let me add a couple of more. There are two super thin gaskets that separate the diaphragm from the horn body. They "seem" to help the amount of sound emitted. Many times horns that have been taken apart did not have the gaskets reinstalled. There was a reason Henry had them there. Model A suppliers carry the gaskets.

Second, the horn works by grounding which is done at the horn button. At the bottom of the horn rod (where it connects to the Bakelite terminal plate), is a soldered tip. Make sure this tip is super clean to insure a good contact. Too often this area is gummed-up due to the gear box leaking and hence a bad grounding contact.

Tom

 

[jfcrash]

Tom,

With time passing and your suggestions comes a few questions…

Two gaskets per horn? I can see where one would easily go…are you saying to put one between the diaphragm and the horn motor body also?…. looks like the pole bolt would have to be removed and is the threaded part for the point adjusting nut and lock nut all part of the same pole bolt?? Any precautions here?

The horn rod does make good contact and provides ground thru the new main harness to the connection point which the horn motor wire harness will attach…thanks.

Also, does the horn motor wire harness I show passing through the horn mounting bracket have the right electric connectors on them to slip into/under the terminal block as mentioned earlier?

Thank you, Jim

 

[Lawson Cox]

Also, does the horn motor wire harness I show passing through the horn mounting bracket have the right electric connectors on them to slip into/under the terminal block as mentioned earlier?

Yes on the terminals.