Topic: Horn repair

[_mark]

Hi guys.

My Horn is not working anymore even if supply is ok.





I measured the resistance and I got these values.




Can anyone tell me if everything is ok or if there is any way to make troubleshooting ? thanks

[Bailgang]

Clean the point contact with some fine emery cloth of sandpaper, my guess is 99% of horn failure has to do with that contact being dirty or corroded. I'll try to download your pic and circle what it is I'm referring to.

[Bailgang]

The point contact is the area I have outlined in red.

[_mark]

Thanks a lot. I will try and update soon.

[Bailgang]

Keep in mind your pic shows the top of the contact and the area you need to clean is is directly underneath, you'll see what I'm talking about when you look at it from another angle.

[Bodi]

Your 0 ohm reading is the horn's electromagnet coil, not really 0 ohms (or it's really broken!) but fairly low. The 1.5K reading is across the switch contacts. To work, the electromagnet just pulls open the switch contacts and turns itself off, then the contacts spring back closed and turn it back on... this happens a few hundred times a second, making the horn sound.
Cleaning the contact points should revive your horn. You may need to bend the contact arm down a bit to increase the pressure on the contacts, this changes the tone of the horn though.

[_mark]

Hi thanks for the answers I just made photos only.





I did not yet cleaned but is reasonable that 1.5 kohm resistance is too high ? and for sure the contact is dirty or rusted? I cannot understand why 1.5 kohm for a contact... and moreover the two beams are in contact at the base (see copper rivet) i will try to clean but I'm afraid to bend the beam and damage the original stiffness of the horn and so its soud


Shall the contact be closed during rest (not powered position) ?

Your 0 ohm reading is the horn's electromagnet coil, not really 0 ohms (or it's really broken!) but fairly low.

Yes is near zero but not open contact.

[_mark]

Hi i cleaned the contacts, resistance now is very low, not anymore 1.5 kohm, I reclosed the horn but it isn't working.
I stopped the test because I am afraid to damage something.
Considering that the horn is a coil in serie in a DC circuit, is there any danger to damage something with a short circuit ? thanks

[RAFster122s]

What is the horn from Mark, it isn't like my CB550F horn, as it has a chromed cover over the one side and contacts are via wires under the case... I've not disassembled it further.

The stebel Nautilus air horn is quite loud if you want to go that route. Relays to control the horn are a good thing as you can pull power from the battery with the load being from that and the relay switching by the original wires to the horn. Easy conversion and sometimes possible to put a small relay in the headlamp bucket.

David

[mystic_1]

Looking at this picture:



It appears to me like that whole assembly is sitting on an adjustment screw that would let you vary the height of the switch.  The idea is that you need to set this so that the movement of the diaphragm just opens the switch, too far one way and the switch will be open always, too far the other way and the switch will be closed always. 

Try varying the position of that screw (it appears to be all the way "up" in that picture") and see if you can get it to sing.

mystic_1

[CB650CPastor]

Yes! Listen to mystic. He is correct. The center pole piece is also adjustable. You'll see a slot in it on the outside of the horn with a lock nut that also usually holds the mounting bracket. Both adjustments have to be right for the diaphragm to vibrate, and the volume to be maximized. Stay with it. You're almost there!

[_mark]

Thank you I was aware about the adjustable screw.

Cleaning the contact points should revive your horn. You may need to bend the contact arm down a bit to increase the pressure on the contacts, this changes the tone of the horn though.

Now after I bent down the arm the horn is working but the sound is orrible. Next stage I will try to pull but is not easy considering that there is not space to pull arm underneath...

[CB650CPastor]

You shouldn't have to bend the arm! Use the adjusting screw to change the clearance and make sure the contacts are clean. Once you start bending things, you might have a hard time ever getting it to work again. On the bright side, horns are cheap.

[_mark]

You shouldn't have to bend the arm! Use the adjusting screw to change the clearance and make sure the contacts are clean. Once you start bending things, you might have a hard time ever getting it to work again. On the bright side, horns are cheap.

Hi & thanks. Horns are not cheap. best option is a used one 60 euros or a new one around 100 euros (with delivery).
I pulled the 2 arms in my direction and once obtained a good bending of the lower one, I pushed the superior one back in place (not measured, just roughly). This with the aim to have a pre load of the lower one against the upper one and close the clearance.
I rebuilt the paper gaskets (the thickness is 0.5 mm) and now is working vvery good.