Hi all
Heres a strange one
Went to fit some Fiaam horns bought of e- bay to my t3 to replace the working but underwhelming horns already on the bike, bolt em on and connected the wiring as normal( and how the old horns were fitted) IE- brown (I guess live?) wire to the horn + same on the other one!, and the black(I assume earth?) to the other terminals on both horns, when i turned on the ignition SCARED THE **** outa me as both horns sounded immediately WITHOUT ME TOUCHING THE HORN BUTTON!.
Disconnected both horns from the frame bracket ( so they was not earthing through that!) and turned the ignition back on and-nothing did not sound, so then tried pressing the horn button and nothing still did not sound but could here a slight clicking /movement of the horns diaphragms!.
From this i am guessing that the brown wire is a live feed to the horns which is always live when the ignition is on? and the system works by when you press the horn button this completes the EARTH pathway and should sound the horns do you think i am on the right track here? dont know what to try next however when i re-fitted the old horn sets they still operated normally as before!.
The conclusion i am making is that the earth wires between the horns and the button are in some way compromised and have excessive resistance and when trying to sound the (I again assume more powerful and therefore larger current draw Fiaams) they cannot complete the circuit hence just the slight movement of the diaphragms? again assuming the old horns are a much lower draw this is why the system can cope with them? any other ideas gratefully received before i start looking at examining /replacing the wiring to the horn button via spaghetti junction inside the headlight shell!
cheers
Steve
Steve
You are correct the brown wire is the live feed and the black wire is the earth but only when the horn button is pressed.
Have you checked the wiring to see if the black wire goes to earth without the horn button pressed?
Do the Fiaam horns have a wiring diagram with them that shows that they should be connected differently to the original horns?
Hi guys no wiring diagram for the Fiaams as they were used from e-bay!
Checking the wiring back is the first part of the plan. what i dont understand is why the old horns work with the wiring as is!, but the fiaams dont!- hence my comments about resistance etc.
cheers
Steve
I believe I have the same twin FIAMM horns that I installed on my much later of course 2013, and they work perfectly. I still have the instructions in the original box tucked away if you’d like me to take a look. Also replaced the horn on my ‘78 LeMans but that was a duplicate. Hope you have figured it out ..
If you could have a read through and see if ive missed anything( seller has suggested they might need a relay) id be grateful! thanks very much!.
Steve
Steve, - I will attempt to attach the instruction booklet here - hopefully my 70 year old brain will manage it.! The site is saying I can only upload 5 files at a time and there’s 6 pics so please check additional and let me know - good luck mate !
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When I put similar on my Tonti I had a relay, it came with the horns.
Thanks for taking the time to do this for me ! the type d instruction are what i tried when the horns sounded as soon as the ignition was turned on, so i dont reckon that way will work!, i might try the type c method and see what happens if that fails i will do more research into fitting a relay in to the circuit! will let everyone who has tried to help how i get on!, many thanks Steve
Seems like maybe type D method could be your answer Steve but then I’m no electrical expert. Will be interesting to hear how you go on.
Will be sure to let you know! just gotta find some “fiddling” time n 
ow
Steve,
Have you checked in the “ Technical Issues “ section.? 6th row down in the miscellaneous there is a post from @Elek-trickery who has posted a whole article from Gregory Benders “ This old tractor “ - scrolling down to the very last pages there is notes and diagrams on horn replacement / setups. It may be of some use and interest…
Alan : )
On Moto Guzzi’s, the horn button usually makes earth contact to complete the circuit so live power flows into the horns via one wire, it goes through the horns and the circuit is completed when you press the button as that goes to earth.
This is different to the way that most other manufacturers wire them up. You may be better wiring in a relay to operate them.
Iwill try and find it to read when i have more time! thanks mate!
Thanks don already contemplating this if all other options fail! cheers!
Steve
To all who offered advice i have them on and working now! turns out the metal mounting brackets were making a direct earth to the frame which was bypassing the horn wiring!
Its fair to say my t3,s wiring has been “modified!” by various “apes” over the years and is nothing like standard either ! thus thwarting my investigations somewhat.
In the end i got inventive and made a couple of new brackets out of an old Bakelite panel i had in the shed(came from an ancient radio as i recall) which is an effective insulator! hopefully its structurally strong enough to stand the strain time will tell.
These removed the direct horn to frame earth pathway and allowed the horns to operate from the button, without the need for a relay etc- probably not best electrical practice or even a bit of a “bodge” but its working and thats the point for me.
Thanks once agin to everyone for chipping in,Steve
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That is what I said about Guzzi horns being wired differently to all other nanufacturers! It’s not an old bodge, it’s how Guzzi did things back in the 70’s and 80’s.
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You can get nylon isolating shouldered washers that look like a top hat with the lid cut off, they work like a normal washer between the flat surfaces but the tube part fits around the bolt isolating that from the brackets. You will also need a nylon plain washer under the nut.
Beware that your Bakelite brackets maybe brittle and fail.
Best of luck Chris
Hi chris
Yes i agree about the Bakelite’s tensile strength so i wrapped it in gaffer tape before fitting to hold it together if the worst was to happen.
Basically done just to prove i could get then to work on the bike, and as i like things “right” I would be loking into something better overall anyway but like the top hat washer thery so getting over to e- bay now to investigate!.
thanks once again mate.
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