I have finally gotten around to documenting my 2003 530 air horn installation project. So here we go.
Sorry but if you have 8 cylinders; you are going to have to find another space to mount yours. I think you have an air breather where I put the horns on mine. Oh the advantages of the M54.
I chose a 3 trumpet air horn system. I purchased mine for about $48 plus shipping. The Company is Hella and the part is 85100. Not counting your time, you should be able to get out of this project for under $60. Here is the catalogue pic of the part. Note that it only shows 2 trumpets but the 85100 has 3. My other car has 2 trumpets so I wanted something that sounded a little different. Either one will make heads turn when you blow it. The 3 trumpet is a little more melodic but not quite as loud as the 2 trumpet.
I also purchased an in-line fuse and installed a 25 amp fuse in it.
I used 2 sizes of wire. Sorry to say I don’t know the gauge but I’m going to call the high current wire the yellow wire and the low current wire the green wire. The high current wire needs to handle 25 amps. Don’t skimp on materials.
The installation is deceptively simple. It took me several hours from start to finish. Maybe 8. Your mileage may vary. I thought of saying it only took me an hour but I’m a scout. Also you can save some time if you don’t want to be neat with your wiring (not what I would expect from anyone reading this). I was able to use all existing holes for mounting.
First thing I did was to disconnect the old wimpy horns. This is was a pain in the butt as I needed to remove my front bumper. Anyway, once I got the bumper off, I disconnected the horns and punched the wires up into the engine compartment.
Next I mounted the air pump. I used an existing hole and a simple L shaped heavy duty bracket I found kicking around my basement. Nice.
I think this is where I had a cold Labatt.
With the pump mounted, I was feeling some progress. So I moved on to the horns. As you might imagine, my options for location were a bit limited as 3 trumpets take up a lot of room. I would have liked to have mounted them closer to the outside to avoid muffling the sound, but ended up compromising by choosing the position I did. On the bright side, they are well protected from the elements. Again I was able to use an existing hole.
Next I bent up a simple bracket from scrap. I drilled it and painted it.
Here you have a pic of the horns mounted. Sweet.
The only other component I needed to mount was the relay that comes with the kit. If you look carefully, you can see the relay here, once again using an existing hole for mounting.
Now for the wiring. As you may have guessed, I got a C in electronics. The relay has 4 connections.
I’ll explain where the most interesting wires connect. You can read the instructions for the details.
First is the low current green wire that is energized when you push on the horn button. This is taken from either of the purple (not brown) wires from the original horn connectors. I just snipped one of the purple wires to make the connection to my green wire. I then taped the other old horn connections up to keep them clean and tucked them neatly away. I ran the green wire around the back of the firewall and over to the relay. By the way, I left the old horns intact. Sort of like keeping your testicles after a vasectomy.
Note there is a plastic molding strip that pulls off of the top of the firewall. With that off, you can tuck wires down in there to keep your install neat. You will also need to wrestle with the air cleaner and the electronics boxes in the rear corners of your engine compartment to aid in your wire tucking. At least I did. The result was worth it.
For the high current yellow wire, I connected directly to the jumper spot for + as shown below. Very important is that I placed the fuse inline as close to the jumper point as possible. The fuse is hidden behind the firewall as shown. Remember that you have a lot of juice in the + wire. Please be careful.
OK. I’m getting tired. The other interesting connection point is for the ground. The relay needs one and the motor needs one. I took the ground directly from the – jumper point as shown:
Now with all your connections made and the horn should be ready to blow. In summary your install should look something like this:
Good luck and God’s speed to all who attempt this little exercise.