How to: Mazdaspeed 3 Hella Supertones install (pic heavy)

So I was encouraged by our fearless leader (Raider) to do a write up with pics on this install since he informed me this forum doesn't have this particular install yet.

Full disclosure, I have zero confidence with wiring and did as much research and reading as I possibly could before digging in. I take zero credit for this post except for simply trying to educate you folks. I looked on other forums and took bits and pieces from those posts and applied it to my install.

From our own MSO's Raider on MazdaSpeed forums
MazdaSpeed Forums / Marchy
Legacygt.com forums/ j.reed
TorontoMazda3 / yearoftherat (i used this one alot)
If you google "hella supertones install mazdaspeed" you'll find the same posts I referenced

What I saw alot of people like to do is mount them in plain view from the front of the car for aesthetics, but since I just wanted to make life easier for myself and my tool and supplies resources were limited somewhat I mounted them in the stock horn location.

Supplies:
Wratchet set with extensions
Crimpers
1 20' reel of 14g wire
blue ring terminals
blue butt connectors
blue male and female connectors
lots of electrical tape
lots of heat shrink tubing
Self tapping screws
M6 x 20mm stainless steel bolts with nylon lock nuts

So, here we go.

Start by getting the front of the car up in the air and removing the left front tire, then removing all the clips and fasteners that secure the fender liner. I didn't remove the whole thing, just the front portion then pulled that back and behind the brake rotor.



After you get that out of your way there is another splash guard inside of that, it's kind of tricky to remove if you do this with that whole front fascia on like i did. Just trying to make it easier for myself. You can see where the fastener is, pop it out with a flat head screwdriver and pull it out of your way.



So now you've exposed the oem horn. There's just one electrical clip, pop that off, and one bolt securing the horn and bracket to the chassis. With one nut holding the horn to the bracket. Remove everything.


Now for what I would consider the hardest and most time consuming part: Figuring out how to mount everything up. I took the stock horn bracket and modified that for one horn, then took two of the metal mounting brackets (6 total) that came in the box with the new horns and used two of those.

I took the stock bracket and took two pairs of vice grips (I don't have a bench vise) and twisted it so the horn that I mounted to it would be facing backwards from the front. This is the only way to have proper clearence for both horns in that tight location since they are quite a bit larger than the old one. This worked out really well!


Next we mount the 2nd horn, here you can see where I mounted that one, like I said I took two of the metal mounting brackets that came with the horns and bolted those to the chassis. I used a stainless steel bolt size M6x20mm with a stainless steel nylon nut on the backside to bolt that one in. It is tight quarters right here with two ratchets on both sides to tighten it down so just be patient.


After I got everything mocked up and how I wanted them mounted I prepared my wires. Be sure you're slipping your heat shrink tubing onto the wire before you crimp your connector or you'll need to make a new piece of wire.

First I made my two ground wires for the horns. Take two 7" pieces of wire, at one end crimp a blue ring connector, then secure it first with electrical tape then heat shrink tubing. At the opposite ends, crimp 2 blue female connectors, again secure it with electrical tape and heat shrink tubing. This end connects to the gold terminal on the horn.


Next, is preparing the wires that will connect to the silver horn terminals. I took two pieces of wire 7" long, strip some wire on both pieces and twist the wires together in order to be able to attach a female connector to them, electrical tape and heat shrink tubing again. Remember to slide your heat shrink on before making your crimps and taping. At the other end, strip and crimp another blue female connector, tape and heat shrink. This end will connect to the 87 terminal on the relay.


Next, I made my wires for the power and ground. For both I took a very long piece to run from the battery and ground bolt on drivers side fender. For the ground, strip,connect and crimp a blue ring terminal. I ran that wire down inside the fender and tried to conceal it as much as possible. This will connect to the 85 post on the relay.


For my power wire I took and piece of wire and had to splice in a a 20amp inline fuse holder to connect to the positive battery terminal using a blue ring connector. (kudos to raider for his guidence in this part of the install)


(sorry for the poor quality, didn't realize it at the time)

There's a hole in the bottom of the battery box I used to run my hot wire out of. Then tucked it up between the shock tower and fuse box, then joined it with the ground wire with zip ties and ran that like the ground, down and inside the fender. At the opposite end of your power wire you'll connect another blue female connector, again, tape and heat shrink. That will connect to the 30 post on the relay.


Here is the hot and ground peeking from the bottom after I had cut them to length and made my connectors after deciding where I would put my relay.


Now that I've got my wires run, I had to completely remove my two horns in order to be able to connect my grounds.
I didn't want to drill new holes for the horn grounds, there are 4 small factory holes on the bottom side of the bumper support beam, so I took two large self tapping screws and used two of those holes and made my connections there for the grounds.
This perspective is looking up, on my back from the floor. (NOTE THE HID BALLAST IN THIS PIC)



Next I started making all my connections. Since the stock horn wire was a tad short, which connects to the 85 post on the relay, what i ended up doing which worked out quite well, was I took two zip ties and tied the relay to the hid ballast. (No more pictures beyond here, I had used all available space)

After I made all my connections to the relay, check and double checked everything I reconnected the negative battery terminal and gave it a try. I was shocked it worked like new on the first attempt. I about blew out my ear drums they are so loud.
So now that I confirmed they worked, I tied up all my wires and made everything neat and tidy. I probably went overkill with the weatherproofing but I absolutely didn't want to go digging around again trying to fix something. I was actually really pleased I did this myself with no backtracking involved.

Some people did this in just a couple hours, but I spent literally all day with this. I just took my time and made sure I was understanding everything thoroughly. If a complete noob like myself can do this, then so can you.
JUST NUT UP and GOOD LUCK!

 

Looks great! Thanks for writing this up!

 

Overkill. just run wiring, use a male connector, and hook into stock horn connection. You do not have to run a hot wire to the battery. There is a 15amp fuse already for the horn. Loud as shit too.

 

I had two similar relays that failed on my horn setup (Cadillac 4-note) due to corrosion of pins, so now I run waterproof version.