Wolo Air Horn System

The installation and wiring for my aftermarket air horn system is rather complex, so I'm putting this page up to document it. I decided to install something I could cleanly expand to include other possible electrical accessories without creating a rat's nest of wiring.

Wolo Air Horns

I bought a "415-MC Airsplitter" direct from the "motorcycle horn" section onWolo's web site. The compressor is about the size of a soft-drink can. The horns are metal. They cost $86 for the kit, including shipping.

On the SV-650, I mounted the horns on the Givi side racks using some small L-brackets that I made. I used the plastic "snow cones" to keep debris out since they're out in the open. They're inboard of the racks so they're hidden when there are bags on the bike. I mounted the compressor under the passenger seat and drilled a 1/2" hole for the air line.

I mounted the compressor and horns inside the fairing on the DL-650 using rubber coated electrical wire brackets. I removed the snow cones since the fairing protects the horns from the weather, and they're pointing down anyway. I mounted the compressor itself using a worm clamp and a small piece of fuel line to protect the bracket on the bike.

ISO (Bosch) Standard Automotive Relay

The horn compressor draws nearly 20 amps, which is a lot of current. A relay is needed to protect the stock horn switch and wiring. If it's not used then the horn will not be nearly as loud due to the resistance of the small wire, and there's a good chance of burning up the wiring or spark-welding the switch contacts together.

These are standard 4 or 5 pin relays packaged in a 1" cube with a small mounting tab. They're available at most auto parts stores. If it has a 5th pin (87a), it may be either a duplicate output pin tied to pin 87 or a reverse of the output pin as in the circuit diagram below. There's usually no way of telling from the retail packaging. Other than that, the pin configuration is standard. A 4-pin model is fine for this application. One of these is supplied with the Wolo horn kit.

Putting a small current across terminals 85 & 86 energizes the coil, which then pulls in the pole that connects the common pin 30 to the output pin 87, and disconnects pin 87a if it exists. Note that these are standard pin IDs. This style relay is usually rated for 30 amps, which gives us a comfortable margin.

Wire

Instead of the usual single-strand automotive hookup wire, I used black household 14-gauge two-conductor "zip" wire like the stuff used in 120VAC power cords. This provides ample current capacity to handle the high draw from the horn compressor. In the DL-650, I needed two runs under the fuel tank: one from the horn output behind the radiator back to the impulse relay, and one from the ISO relay to the compressor in the fairing. Using the zip wire made this very easy, as I only had to deal with one line per run. Since it's high-quality multistrand copper, it's also very flexible. This stuff is available from any Ace/Home Depot/Lowe's style hardware or building supply store. Another advantage is that it's dull black, not shiny like standard plastic-coated automotive wire, so it's invisible.

Suzuki uses standard 0.25" male tab connectors on the stock horn, so I used standard female spade connectors that fit, and connected this to the silver tabs on the impulse relay. I didn't do any cutting on the stock wiring harness and I can reinstall the stock horn. The horn on the DL-650 is extremely difficult to access under a plastic shroud behind the radiator.

Since the compressor in the DL-650 was in the removable fairing, I added a Molex connector in roughly the same location as the stock wiring connector.

Impulse Relay

The need to continuously hold down the horn button significantly reduces the driver's available options. Being able to just push the horn button and have the horn stay on frees up the driver'sshooting throwing clutch hand and makes dodging idiots easier.

I didn't want to replace or alter the stock switch. I searched the Internet for a simple circuit that would operate on 12VDC and provide a toggle function, and I didn't have any luck. Oh well, I really didn't want to have to solder together a circuit anyway. That stuff never works for me.

I finally settled on using a Potter and Brumfield S89R impulse relay, part #PB514-ND for $37 from Digi-Key. This is a device that toggles between off and on when pulsed. This is quite different from a latching relay which sets with a current to one pole and resets with a current to another pole.

It operates by having a solenoid pull in a pole that trips a cam that operates a pair of standard lever switchs bolted to the side of the solenoid frame. It's large, expensive, and somewhat of a mechanical hack, but it works and seems to be reliable. Since the rating is only 5A, it'll drive the existing ISO relay.

In the picture, the silver tabs connect to the solenoid coil and the copper tabs are on the output switch. My particular unit has two switches on it, but I just use the one.

Fuse Block and Ground Bus

By the time I was going to install the impulse relay, all the auxiliary wiring in the SV-650 was a mess. Everything had its own dedicated full-size or mini blade or even a round glass fuse, located somewhere along the hot part of the circuit. There was a half-dozen connector rings stacked on the battery terminals. Every time I touched the battery it was a hassle, and it also reset the tripmeter and alarm back to defaults. Something needed to be done.

I found a 6-circuit fuse block at an auto parts store that takes standard ATC fuses. I would like one that takes the mini-blade fuses that the bike uses, but I can't find any. Each auxiliary circuit gets power from one of the tabs, and there is only one wire going to the battery positive terminal. Now all the fuses are easily accessible in one place and are one standard type.

I also added a master ground block made from an 8-position terminal block (Radio Shack #274-670) where one side has been connected into one circuit using a metal jumper plate (Radio Shack #274-650). Each circuit is grounded to one of the terminal screws, with only one wire going to the battery negative terminal. This is especially important on the DL-650 because the frame is made from steel and aluminum, and using it as a ground will cause galvanic corrosion between the dissimilar metals.

Circuit Diagram

Flikr Photo Set

Mounting of compressor and horn in DL-650 fairing

Wiring under SV-650 seat

Wiring under SV-650 seat

Note that the wires are left long so that the tray can still be removed for access to the battery.