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Hooking Up extra Horns
By Chet Walters
This works on any bike, these instructions are for Honda Valkyrie

I first installed a pair of NIKKO horns (Dual Chrome YPD1400-12 [K32-7502] from Crossroads 1-888-632-8709) under the swingarm with a relay (if you don't understand how or why we use a relay, see below for a very basic explanation). I have since replaced the Nikko's with a set of horns from a Dodge Caravan (Chrysler horns are always VERY LOUD) that I got at the boneyard for $5.00. Same location. Easy to do. The relay serves to sound the extra horns in addition to the existing horn on the bike. The installation is rather straightforward, and you may well want to mount the Nikko horns elsewhere since they are so attractive (a buddy has them on the crashbar on his InterState where they look good). They can be mounted to an empty hole in your motor mounts on either side, like I have my Shadow Horns mounted, or you can even mount them between the forks under the triple clamp using Rattlebars UnderWhere. In addition, we will give a beginners lesson on using relays for this and other things.

TIME: 60 minutes

NIKKO Dual Chrome Horns
14-16 gauge wire
4 splice-in wire connectors (blue plastic variety)
6 female quick disconnects (Radio Shack 64-3049)
1 male quick disconnect (Radio Shack 64-3049)
1 Standard Duty Relay (Auto Zone $4.69)
or Radio Shack "Auto Relay" ($5.98)
1 in-line fuse holder with 15 amp fuse
weather resistant electrical tape
It depends on where you want to mount them

QUICKLY FOR THE EXPERT: Supply a fused +12V through the relay to your horns. Activate the relay with the hot wire from your existing horns.

QUICKLY FOR THE MOTORHEADS: See the drawing. The CHEAP relay relieves your EXPENSIVE horn switch of any danger of burn out.
NOTE: this is a "layman's" drawing which shows only the terminals on the various parts. It is intentional that there are no electronic symbols included. The terminal numbers shown are from a typical relay, yours may vary.

FOR THE REST OF US: You will actually have to decide where you want to mount these attractive horns. I mounted mine under the swingarm. I don't yet know how long they will last there since it's dirty and "unsprung", but since they are only $35, I should get my money's worth out of them.

Under the swingarm up near where it mounts to the frame there is a large empty area covered by a pad of sorts. Hold your horns up to the pad with the "mouths" pointing toward the front of the bike and mark the two holes in the mounting bracket. Drill two holes at the marks through the bottom of the arm. You will drill first through the pad and then through the arm, which is hollow so only drill through the bottom part. Mount the horns with lag screws, or if you're good, tap the holes and use machine screws. It's a good idea to seal the screws with silicon. For a pic of the installation, click here.

Wire according to the drawing. If you would like your turn signals to light up in conjunction with your horn beeping (see Horny Lights) then if you use a relay like here, you can hook directly to your signal circuits with diodes as shown and can skip the relay shown on that page. You should hook a switch up for these in front of the diodes in case your state does not allow blinking of lights as cautioned on the Horny Lights page.

But, why do we need a relay??

Some may not know what a relay is or how it works. Maybe a little parable. There once was a little man named Jon whose job it was to lift a weight of 50 lbs. He could do this all day long with no trouble. But, one day the boss came up and said that Jon now had to lift 200 lbs. But Jon knew he could not lift 200 lbs without eventually breaking his poor little back. So, he got his friend, Hercules to lift the 200 lbs each time that Jon tapped him on the shoulder. So Jon was able to lift the extra weight through Hercules' strength and Jon did not have to lift any weight at all.

Let's say you want to add some extra horns to your bike. Your horn switch (Jon) was designed little but it only had to supply current (50 lbs) to your dinky little stock horn and can do that easily. However, your new horns are bigger and require more current (200 lbs). If you simply hook up the new horns to your existing wiring and switch, then your switch will burn out rather quickly. How to get around this? Install a relay (Herculese). A relay is a mechanical or solid state SWITCH which is triggered (tapped on the shoulder) by current supplied to its trigger terminal (86). When current hits that terminal it closes the switch inside the relay, be it mechanical (by energizing a coil magnet) or solid state (by tripping a transistor). The other terminals of the relay then feed current from the INPUT terminal (30/51) through the now closed contacts to the OUTPUT terminal (87). Your old horn switch does not feed current to your new horns, it only triggers the switch inside the relay. The switch inside the relay feeds current to your horns from a completely different source (ie battery).

To wire up your new horns so that your little switch can work them, wire them as illustrated. Your old horn wire that went "hot" when you pushed the horn button is hooked to the TRIGGER terminal (86). When you hit the horn button, the button only needs to supply a small amount of current to trigger your relay. Hook up heavier wire thru a fuse directly from the battery to the INPUT (IN) terminal (30/51) and then hook your new horns "hot" to the OUTPUT (OUT) terminal (87). Terminal 85 is common ground (you can use your old horn ground). Now, instead of asking your weak and EXPENSIVE horn switch to work the increased load, your strong, CHEAP and easily replaceable relay does all the heavy lifting. (Click here for more info)

Relays will also fail after a time. Some are even rated by the number of times they will close a circuit before burning out (common relays are usually rated to 100,000 operations). The advantage is that a relay is normally cheaper and easier to replace than a switch. Using a relay also allows the use of smaller guage wire to the switch as well.

A common auto relay is shown above along with the functions of the terminals.

One should note that many relay packages are incorrectly labeled. The package that this relay came from labeled terminal 87a as "power to lamps" just like 87 when the 87a terminal is actually "normally on" and goes cold when the relay is triggered. One should test these terminals to determine what each actually does before making a permanent installation. Usually, if the center terminal is labeled ON THE RELAY as "87a" then it is usually a normally on terminal and will go hot (complete the circuit with terminal 30) when the trigger is cold. If it is also ON THE RELAY labeled as terminal "87" then it will usually be a normally off just like the outer 87 terminal. These 87 terminals can be used creatively as input to feed current from two sources to the 30 used as output. Details on use of these terminals in this reversed fashion can be found at One should always mount a relay of this type with the terminals down and it helps to seal the seams around the case and terminals with silicone seal. These relays are sensitive to moisture and they will corrode if directly exposed.

Another type of auto relay (Conduct-tite #84607) is shown here.

One should test these terminals to determine what each actually does before making a permanent installation. Terminals on this three post relay are labled here with the functions of the terminals matched to the more common 4&5 post relay above. These terminals are not interchageable and the case provides the ground. This relay appears very similar to a typical auto horn relay, but most auto horn relay completes the ground circuit and is unusable in other applications. One should always mount a relay of this type with the terminals down and it helps to seal the seams around the case and terminals with silicone seal. These relays are sensitive to moisture and they will corrode if directly exposed.

This mod can be performed on any modern motorcycle which employs the same circuitry: Find the horn hot wire and suitable horns.
Questions? Contact Chet at Chet says 'Be sure to write!'

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