Misc: Everything Else Horn Switch Confusion

[danno]

Hi
I’ve just finished sorting out the indicators on my C Rapide and now the horn is blowing the main 35a fuse.
There was a stray black lead in the headlight so have traced that back to the horn switch and
have connected it to a non switched 12v supply on the ignition barrel.
Ideally would like to have the horn working only when ignition’s on but it’s always been like it.

I have a 3 way switch fitted on the handlebar with the live feed to the lower right terminal and the negative to the one just above it.
The horn button makes contact with this one but if the small button underneath is pressed, the main fuse blows.
Not sure what this one is for but have spent some time trying to figure in out. Pics show the switch.
The bike has postitive earth and electronic ignition.
Any ideas appreciated.

 

[Gary Gittleson]

All the horns I have ever worked on had a 12v feed to a terminal on the horn itself and a lead from the other terminal to the button on the switch. That button completes the circuit to ground. So connecting 12v to the button will cause a direct short to ground when the button is pressed.

 

[oexing]

Is the horn the one connector type or two connectors type ? If one terminal on horn the handle bar switch has to send current to the horn which gets the earth from its housing and via the earthed handlebar to the rest of the bike.
In case of two connectors on horn it gets direct power from the harness and sends the exit to the handlebar switch and when you press the switch it gets earth for completing the circuit .
Anyway, provide an extra earth wire for headlamp and handlebar from the battery and rest of bike as you don´t want to lead all high current through your fork ball bearings .

Vic

 

[danno]

In case of two connectors on horn it gets direct power from the harness and sends the exit to the handlebar switch and when you press the switch it gets earth for completing the circuit .

Yes, two connections.
It’s ok until that small button underneath is pressed.

 

[danno]

All the horns I have ever worked on had a 12v feed to a terminal on the horn itself and a lead from the other terminal to the button on the switch. That button completes the circuit to ground. So connecting 12v to the button will cause a direct short to ground when the button is pressed.

Thanks.
Just need to get my head around it. Always has worked ok.
In this case, both cables go to the switch rather than one direct to the horn terminal.
Also it’s in contact with the handlebar through the lower securing strap as it touches the brass bit inside.
Maybe would be ok if the switch cluster was isolated from ground.

 

[b'knighted]

“There was a stray black lead in the headlight so have traced that back to the horn switch and
have connected it to a non switched 12v supply on the ignition barrel.”

The problem appears to be that you have connected the “stray“ wire to a live supply. Disconnect it. If everything except the horn now works it would suggest that it shouldn’t be connected to live. There is a good chance that it should be connected to earth to make the horn work.

The terminals shown in your switch are physically contacted by the lever. Wire both middle terminals that are contacted in the indicator off position to live feed, possibly through a flasher unit, then top to right indicators, bottom to left. If the two terminals on the right of the switch are contacted by a horn button in the cover, one goes to the horn, the other to earth assuming that the horn has a constant live feed.

If you want to disconnect the horn live feed when the ignition is off you'll need to add a relay in it’s feed.

 

[chankly bore]

Some horn/ dipswitch combinations had an ignition cutout on them as well. Perhaps you have connected this in error. Vincents were not fitted with this type of switch.

 

[danno]

“There was a stray black lead in the headlight so have traced that back to the horn switch and
have connected it to a non switched 12v supply on the ignition barrel.”

The problem appears to be that you have connected the “stray“ wire to a live supply. Disconnect it. If everything except the horn now works it would suggest that it shouldn’t be connected to live. There is a good chance that it should be connected to earth to make the horn work.

The terminals shown in your switch are physically contacted by the lever. Wire both middle terminals that are contacted in the indicator off position to live feed, possibly through a flasher unit, then top to right indicators, bottom to left. If the two terminals on the right of the switch are contacted by a horn button in the cover, one goes to the horn, the other to earth assuming that the horn has a constant live feed.

If you want to disconnect the horn live feed when the ignition is off you'll need to add a relay in it’s feed.

Thanks, that's helpful.
It must be that stray wire connection as suggested.
Some of the Lucas bullet connectors did come off while wiring for the indictators.
I made a note of where everything goes but noticed the black unterminated
lead from the horn switch.
It's connected in the cluster so must be for something.
I'll try it to earth instead.

 

[danno]

The problem appears to be that you have connected the “stray“ wire to a live supply. Disconnect it. If everything except the horn now works it would suggest that it shouldn’t be connected to live. There is a good chance that it should be connected to earth to make the horn work.

Seems to be working ok now with the lead disconnected. Reconnecting to earth doesn’t make any difference so not sure if it was connected to anything or why it’s wired in.
From what I can make out, the small sprung button on the underside (maybe ignition cutout as mentioned) breaks contact with earth and makes contact with the horn button terminal when pressed,
Bit confused how it works but it does.