HELP WITH HORNS

[canuck750]

I need help getting a pair of Fiam 12v horns to work. These are on my Laverda SF1, there are two horns that are attached to a 3 prong relay.

The handlebar switch is the same Nippon Denso switch that is used on a Suzuki GT750 and many other motorcycles from the 70's.

The switch has a horn press button that grounds the wire attached to the end of the sprung button. This ground wire extends down to the relay.

A 12 volt wire that is energized when the ignition is ON attaches to the relay and the third lug on the relay takes wires to the horns. The horns ground to the frame through the centre mounting studs.

I have tried two Fiam relays and a Royal Enfield relay with the same B H and S terminals.

In each case when I press the horn button there is a click and nothing else.

I tested the horns with a jumper wire from the battery and the horns work fine.

I  have gone through the horn switch several times, the wire from the switch is not shorting out and the power lead is reading 12 volts.

Any ideas???

[rodekyll]

I'd wire to a standard 4-prong horn relay.

[wirespokes]

I've never worked with a 3 pin relay, so don't know how they're configured - but I'd guess the horn button provides a path to ground. Is that right?

If the relay terminal to the horn button is hot, then that's how it should be.

Let's trouble shoot the relay to determine if it's a connection or the relay.

What do B, H and S stand for? I'd guess B = battery. H = horn. S = switch.

That wasn't so tough.

Does S have +12V on it when it's activated? Ignition on, and all that.

Jumper a ground lead to S, the horn button terminal on the relay. If the horn honks, you know there's a problem somewhere down-stream in the wires, horn button or the ground connection.

Because you tried two other relays, my guess is something wonky on that line. 

[Wayne Orwig]

In each case when I press the horn button there is a click and nothing else.

When you say 'there is a click', do you mean a faint click from the relay, or a louder TICK for the actual horn.

If it is a faint relay click, you need to look into the relay wiring or replace the relay.
If you are getting a click sound from the horn, you may simply have too weak of a cable feeding power from the battery to the relay. Horns can take a pretty healthy amount of current to pull in initially.

[Kiwi_Roy]

I'm with Rodekyll, you meed a 4 pin relay.

With a 4 pin relay you can run a 15 Amp circuit from the battery to the relay contact a wire from the other relay contact to the horns and a ground from horn to chassis (unless one terminal is already grounded)
The relay coil can then be fed from any handy switched circuit via a wimpy wire with another wimpy wire to the horn button.
Don't skimp on the horn wire, #14 at least. The coil wires can be any small wire.

It can be done with 3 terminal relay but then you need to feed the relay contact with a switched circuit from the ignition switch which or the horn will be always alive. The horn will not be as loud fed from the switch.

BTW the pair of Fiaam El Grande horns from Canadian Tire come with a relay.
ttp://www.canadiantire.ca/en/pdp/el-grande-twin-red-electric-horns-0202005p.html#srp

[Chuck in Indiana]

I'm with Rodekyll, you meed a 4 pin relay.

With a 4 pin relay you can run a 15 Amp circuit from the battery to the relay contact a wire from the other relay contact to the horns and a ground from horn to chassis (unless one terminal is already grounded)
The relay coil can then be fed from any handy switched circuit via a wimpy wire with another wimpy wire to the horn button.
Don't skimp on the horn wire, #14 at least. The coil wires can be any small wire.

It can be done with 3 terminal relay but then you need to feed the relay contact with a switched circuit from the ignition switch which or the horn will be always alive. The horn will not be as loud fed from the switch.

BTW the pair of Fiaam El Grande horns from Canadian Tire come with a relay.
ttp://www.canadiantire.ca/en/pdp/el-grande-twin-red-electric-horns-0202005p.html#srp

hey, Roy.. do you have a picture of your El Grande horns on the V11S? The Mighty Scura's "joy buzzers" are all rusty..

[canuck750]

I'm with Rodekyll, you meed a 4 pin relay.

With a 4 pin relay you can run a 15 Amp circuit from the battery to the relay contact a wire from the other relay contact to the horns and a ground from horn to chassis (unless one terminal is already grounded)
The relay coil can then be fed from any handy switched circuit via a wimpy wire with another wimpy wire to the horn button.
Don't skimp on the horn wire, #14 at least. The coil wires can be any small wire.

It can be done with 3 terminal relay but then you need to feed the relay contact with a switched circuit from the ignition switch which or the horn will be always alive. The horn will not be as loud fed from the switch.

BTW the pair of Fiaam El Grande horns from Canadian Tire come with a relay.
ttp://www.canadiantire.ca/en/pdp/el-grande-twin-red-electric-horns-0202005p.html#srp

Thanks Roy!

Can I use the original switch that is a ground to frame?

The click I hear is coming from the relay, with each of the three relays the same click, I opened up a FIAM relay and when I pressed the horn button the points contact closed but that is all that happens. Horns work just fine with jumpers to the battery.

[rodekyll]

Run a new wire from the horns to the relay and see what happens.

[wirespokes]

A relay is an electrically operated switch. Two of the connections on the relay are for the switch control, the other two deliver the power to the device being energized (horns in this case). They normally have a diagram on the side of the case letting you know what each terminal does.

I've never used a three terminal relay, so if the other guys say they don't work, I'll have to take their word for it. But I can't imagine they'd still be sold if they don't. With yours, you've got two possible reasons it's not working: 1. the relay isn't being activated by your switch, or 2. the relay isn't transferring the power to the horn.

Like I said before - if you ground out the relay at the S terminal and the horn works, you'll know it's the horn switch on the bars. That's an easy enough test to do.

Scenario #2 - replace the relay.

Or you can install a 20amp four pin relay. You will need to mock up a +12V lead to the relay for one of the two horn switch terminals.

Your horn button will work just fine - as long as it makes a connection to ground when pushed.

 

[Kiwi_Roy]

Thanks Roy!

Can I use the original switch that is a ground to frame?

The click I hear is coming from the relay, with each of the three relays the same click, I opened up a FIAM relay and when I pressed the horn button the points contact closed but that is all that happens. Horns work just fine with jumpers to the battery.

Yes, one end of the coil will be connected to a switched circuit, the other end will go to the horn button, when you press the button the coil will have 12 Volts across it.
The reason for feeding the coil with a switched circuit is so when the key is Off the horn won't work.
 

[canuck750]

Yes, one end of the coil will be connected to a switched circuit, the other end will go to the horn button, when you press the button the coil will have 12 Volts across it.
The reason for feeding the coil with a switched circuit is so when the key is Off the horn won't work.

Hi Roy,

The power to the horns is switched, here is the wiring diagram.

I installed a new diode #61 as indicated on the schematic (not sure that has nay bearing on the horns). Replacing the diode made no difference.

When the key is ON power if fed to the relay. Pressing the horn button on the left hand switch grounds the wire from the relay to the horn button.

[Kiwi_Roy]

A relay is an electrically operated switch. Two of the connections on the relay are for the switch control, the other two deliver the power to the device being energized (horns in this case). They normally have a diagram on the side of the case letting you know what each terminal does.

I've never used a three terminal relay, so if the other guys say they don't work, I'll have to take their word for it. But I can't imagine they'd still be sold if they don't. With yours, you've got two possible reasons it's not working: 1. the relay isn't being activated by your switch, or 2. the relay isn't transferring the power to the horn.

Like I said before - if you ground out the relay at the S terminal and the horn works, you'll know it's the horn switch on the bars. That's an easy enough test to do.

Scenario #2 - replace the relay.

Or you can install a 20amp four pin relay. You will need to mock up a +12V lead to the relay for one of the two horn switch terminals.

Your horn button will work just fine - as long as it makes a connection to ground when pushed.

It's not that a 3 terminal relay won't work, given a good feed from the battery it will make the horn go just fine, but if you want to disable the horns when the key is off the power has to go from the battery, up through the switch, back down to the fuse block then to the horn relay, the horn will be much quieter.
With a 4 terminal relay power can go from the battery to a fuse, to the relay, to the horns, you need to get the least resistance possible between battery and horn for it to work best.. I suspect the horn current spikes over 30 Amps. Use a 15 Amp fuse.

[canuck750]

The three pole relay would not work regardless of what tests I tried.

I fitted a 4 pole relay, as per Kiwi Roy's detailed and excellent instructions ran a 12 gauge wire with in line fuse from the battery to the relay, used the switch wires and voila a nice pair of very loud horns!

Thanks guys, I can now get a inspection done and get this Laverda on the road for spring

Cheers

Jim

[twowings]

Ta da!! Good going...