Upgrading To An Air Horn

I started by installing a relay for my stock horn. I didn't really think the stock horn needed a relay, but I have a relay and wires and connectors around as well as a scoot that is already apart where I need it to be. I also want a beefier horn at some point, and this way I'm ready for it when I get one.

I am using a 30 amp SPST (single pole, single throw) Bosch relay. You can get 12V 30 amp relays at most parts stores or Wally World. If you really wanted to be loud, you could use a SPDT (single pole, dual throw) relay to control two horns. Save the package your relay comes in, it will have a diagram showing you which terminal connects to what.

Here's what I'm starting with.

I noticed that there is an empty threaded hole in this bracket, which I believe is where my alarm siren used to be mounted.

The bolt I removed from the alarm brain mounting bracket (another project) fits nicely here. I think this is an M6x1.0 bolt, with a 10mm head.

I mount the relay, but don't tighten the bolt all the way.

Now I disconnect the red/white wire (+) from the horn, but it is not long enough to reach my relay.

I'll need to add some wire to make it reach, so I strip the insulation back on the red/white wire.

Then I make an extension with a female terminal on one end and bare wire on the other. I used 16AWG wire for this.

Twist the red/white wire and it's extension together, solder, and heat shrink.

Connect this wire to the switch terminal of the relay.

Now I need to connect the + terminal of the horn (the one I just took the red/white wire off of) to the output/accessory terminal of the relay. I use 14AWG wire with a female terminal at each end for this.

I extended the brown gorund wire from the horn, as I did with the power wire, and connected it to the ground terminal of the relay.

I ran a 12AWG ground wire from the horn's negative terminal to the frame, where the relay mounts.

Now I need a 12V+ battery power wire. I had a starter wire hanging on the wall that is around 10-12AWG so I decided to use it.

I cut the terminal off of one end and left the other to attach to the battery terminal.

I took the protective tubing off of the cable and heat shrinked the terminal, then put the tubing back on.

Now I needed a place to run the cable into the battery well, so I chose a spot and drilled a hole (I didn't even pay attention what size bit I used, somewhere around 3/8"). Make sure there are no wires behind the spot you are going to drill.

Then I chose a rubber grommet that would fit the hole I drilled and around the + wire, and slipped it onto the wire.

Next, I ran the wire through the hole (starting with the end of the cable without a terminal) and then slid the grommet down and pushed it into place.

The wire should easily come out into the front area where you can pull the slack out of it.

I cut the wire to an appropriate length and added a female terminal. Then I attached it to the 12V+ terminal of the relay.

EDIT : I picked up a fuse and installed it in the 12V+ cable between the battery and the relay. I knew I needed it originally, but didn't have one lying around. I used a 25 amp fuse.

I used wire ties to secure everything and make it look better, and there you have it.

I picked this up for about $40 shipped on eBay. It comes with a 30 amp SPST relay and a bolt to mount it.

I disconnected the wires and removed the old horn and bracket, but I planned to use this spot to mount a new bracket.

I used a 5" L bracket from a local hardware store ($1.39) to make my horn bracket. I just cut part of one side off and drilled one hole larger for the Wolo's moutning bolt to go through. I also bent it slightly to set the horn back some to give me more clearance for front/headlight.

Then I mounted the Wolo to the bracket I just made.

I used the same bolt and hole that was used for the stock horn to mount my new horn and bracket.

Hook the wires up, and it's done.

This horn is quite loud. Don't let anyone fool you into thinking it's a train horn as some advertise... but it's no baby scooter horn by a long shot either. My scoot is so loud that I've been told you can't hear my other horn when I'm cruising... I gaurantee you'll hear this "Bad Boy."

I know there are others out there, but here's a vid I just made for you of the stock horn on the Roketa MC-27 (sounds the same as my old one) vs the Wolo Bad Boy.

http://www.youtube.com/watch?v=8zSx52WyX24

I happen to have an SPL meter here. It's not some pro equipment, and only maxes out at 126dB. I thought it may give a nice comparison though.

Stock Scooter Horn
From 4 Inches : 116dB
From 3 Feet : 108dB

Wolo Bad Boy
From 4 Inches : 126+dB (It easily maxed out my meter.)
From 3 Feet : 117dB

Just for fun, and so you understand why you can't hear my stock horn...

My 2 Stroke's Exhaust At Idle
From 4 Inches : 112bB
From 3 Feet : 99dB

Remember, that's just at idle. Don't expect many scoots to be so loud, mine's a piped 2 stroke with 3000+ miles on the silencer.