New Horn Installation

[Chococar]

I installed a new horn in my Elise yesterday, with the help of my good friend, Scott Dayton (who owns a Nobel version of the Lotus 23).

It started with the selection of the horn. Scott ordered one each of three different horns, which we tested to determine which one was loudest, most attention-getting, and possible to install. There was a clear winner: Hella Twin Supertone Horn Kit (the box says 3AG 003 399-801) disk horn set (300 Hz & 500 Hz) made in Germany. The Stobel Nautilus Twin tone Air Horn was about the same loudness, but the Hella disk horns were very annoying and harsh (that’s a good thing). The little Hella Compact Trumpet Horn Kit 400 Hz / 500 Hz electric trumpets weren’t nearly as loud as the other two. Note the photo of the “rejected” horns. (We’ll install the rejected horns on some bigger cars later.)

We decided to remove the stock horn (see photo), which turned out to be a pain. We started by jacking up the car (at the correct lifting point on the passenger side) and removing:
• Passenger-side wheel
• Small plastic splash shield behind wheel
• Large plastic splash shield behind wheel, including unplugging a couple of things that looked like they might be relays (noting that the harness fabric wrap was splitting, so we added a tie-wrap to keep the bundle together)
• Front under carriage cover
• Body part covering fuse box
• Radiator grille on passenger side

With all this stuff removed, we were ready to begin. Removal of the stock horn is a two-person job! Unbolt the oil cooler and oil cooler bracket, and then remove the oil cooler bracket. Then you can slip a skinny open-end wrench beside the oil cooler (if you pull on it), then position it with a long screwdriver poked through the oil cooler grille (requires a flashlight, of course), then with one hand on the horn, you can barely turn the wrench 1/12 of a turn. Then reposition and go another 1/12 turn. After a little while, it’s loose enough that you can (barely) grab the nut with your fingers and dislodge it, causing the nut and washer to drop into a crevice. With some luck and a variety of tools, they can be retrieved and removed. Unplug the two wires and remove the horn. The photo of the RHS horn location shows the holes from the stock horn and the wires, as they were terminated in the stock condition.

We decided to mount the horns to the back side of one of the two bolts that holds the oil cooler mounting bracket to the car. Fortunately, the bolt is “too long”, which makes it just the right length. On the driver’s side, we drilled a new hole in the horn mounting bracket to raise the horn up so it wouldn’t interfere with the front under carriage cover. So the two horns were thusly mounted, one on each side. See the photo of the LHS horn location.

The stock horns have two wires attached to them. The black wire is a ground, and it can be put out of the way and ignored. The other wire becomes the signal wire going to the horn relay. We cut off the connector and soldered a wire to it long enough to reach to the fuse box, where we decided to mount the new horn relay. We found, and installed, a suitable grommet to protect the wire insulation from chafing on the CF piece through which it must travel

We ran a pair of wires from the drivers’ side horn to/through the passenger side horn and up to the area of the fuse box (see photo). We used 14 gauge wire with kynar airframe insulation on it.

The next step was to figure out where to get power. Since my car doesn’t have the touring option, I have two spare 20 amp fuses (for power windows). I noted that my horn wouldn’t work with the ignition off, and decided that would be ok. We cut the fat green wire that comes off position #3 (driver’s side power window), which is downstream from the fuse. We covered the unpowered end going to the non-existent power windows with shrink tubing and tucked it into the wiring loom. We soldered a short extension onto the wire and terminated it with a female spade connector to supply power to the new horn relay.

We terminated the wire supplying power to the horns with a space connector so it could plug into the horn relay. The ground wire from the horns was grounded at the top of the shock tower, using an existing hole. The ground wire continued to the horn relay, where it was terminated opposite the horn signal.

We mounted the horn relay to the outer-most screw holding on the fuse box (see photo). We replaced the two plastic spacers with a single one that was shorter by the thickness of the relay mounting tab. We accidentally pulled the nut out of the housing to which it was attached, so we had to repair that first. That involved removing the housing from the windshield wiper motor, to which it is attached with a tie wrap (!). Then we repositioned the nut (retained with soft rubber – sorry I don’t know the name of this type of fastener) and then reattached the housing to the windshield wiper motor with a new tie wrap.

Finally, we tested the horns. They worked and sounded great! So we reattached all the stuff we had to remove to provide access originally and called it a success. It took the two of us 6 hours, but that included getting set up, unsuccessful attempts figuring out how to remove the horn, retrieving little things that fell down into the bowels of the car, etc.

An important lesson-learned was to stuff a towel under the area where we were installing or removing parts, as they tend to fall, and there are places from which they cannot be retrieved!

Would I do it again? Absolutely!

Thanks to the pioneers who did similar installations before me and kindly posted some notes on this forum.

[Ground Loop]

Nice writeup Choco!

Originally posted by Chococar

· Large plastic splash shield behind wheel, including unplugging a couple of things that looked like they might be relays (noting that the harness fabric wrap was splitting, so we added a tie-wrap to keep the bundle together)

Nope, not relays. That's your alarm unit. It's clipped into a bracket that is rivetted to the wheel well liner.

You can (forcefully) slide it off the bracket and leave it plugged in, or just disconnect the wire plugs and remove it with the liner.

The stock horns have two wires attached to them. The black wire is a ground, and it can be put out of the way and ignored.

I know on some aluminum-framed cars, one is not supposed to pass current through the frame. So even though the frame is grounded, as you found, it's not meant to be a power lead. Does anyone know if this is true for the Elise, or if Lotus also punts current into the frame as a conductor?


Cool mod -- I hope to do the same sometime in the future. After hearing how hard it is to access, I think I might just leave the stock horn in place and find somewhere to mount an 'extra' horn.

[Surferjer]

I wanted to swap my horn, but that sounds like a friggin nightmare! Forget it. I SWEAR that back in August a few people did the horn thing, but simply added another one located in a different place and avoided all the work. Maybe my mind has lost it. That sounds a bit easier. Although I'm considering taking off the front clam just to paint the grillwork-that's probably not so easy, either.

[JimNOLA]

Forgive my electrical ignorance, but why can't you just use the wires from the original horns for the new horns? Why do you need a new relay and power supply?

[Chococar]

The new horns require a relay and different wires because they draw more current, which would cause the stock fuse (7.5 amp) to pop. If you solved the fuse problem by putting in a higher rated fuse, then the stock horn wires would get hot, which might cause some very bad things to happen.

If you want to mount new horns somewhere else, then you need to find the stock horn wire to use as a signal to your new horn relay. I don't know where it runs, so this might, or might not, be easier than finding the wire end at the stock horn mounting location.

[BrokenR1]

What's needed for those annoyingly loud truck air horns you hear on some vehicles? I thought about putting one of those in the rear with a seperate switch. Maybe disconnect the stock horn as I have a bad habit of honking mid corner.

[JimNOLA]

Are there one or two stock horns?

[Miguel]

Originally Posted by BrokenR1

What's needed for those annoyingly loud truck air horns you hear on some vehicles? I thought about putting one of those in the rear with a seperate switch. Maybe disconnect the stock horn as I have a bad habit of honking mid corner.

They need an air source check out this site:

http://www.wolo-mfg.com/

Originally Posted by JimNOLA

Are there one or two stock horns?

Only one stock horn mounted in the left side towards the front of the crash structure, it's a French made Mixo horn TR99 with a grave note.

[fastliz]

Gosh... I would like to swap out my horns for the Hellas, but this sounds like a LOT of work, especially to someone who isn't that knowledgable.

Mike

[darkSol]

Originally Posted by Chococar

The new horns require a relay and different wires because they draw more current, which would cause the stock fuse (7.5 amp) to pop. If you solved the fuse problem by putting in a higher rated fuse, then the stock horn wires would get hot, which might cause some very bad things to happen.

Put a 15amp fuse in there and be done with it. Just how long are you laying on the horn? Even if the alarm is pulsing the horn on-off-on-off I don't believe that the stock wiring is going to have a problem. We're not talking an 80amp starter motor here.

Just my $0.02...

[charliex]

depends on the rating of the contacts of the relay though, might get a lot of arcing and either they'll fuse together or get so dirty they'll stop working, of course changing a relay is a lot easier, and they may be upto the job already

[ChrisB]

Originally Posted by fastwrx

Gosh... I would like to swap out my horns for the Hellas, but this sounds like a LOT of work, especially to someone who isn't that knowledgable.

Mike

Go with the Stobel horn. Much simpler installation...almost a one for one replacement of the stock horn. Mounts in the same place as the stock horn. I don't want to over-simplify the installation process, it is in an awkward to get to place, but it is just one bolt. I think someone on here provided a more detailed description of the installation...a search might find it. Other than mounting it in place of the stock horn all you need to do is replace the stock fuse with a 10 amp one.

It's a dual-tone horn rated at 139db at 4 feet. It sounds appropriate for the car in terms of tone and loudness. You can get one at Griot's for $39.99:

http://www.griotsgarage.com/catalog....2520&SKU=77839

[Chococar]

The only way to save a bunch of effort is to mount new horn(s) in a different place from stock that has better access. The difference between mounting one or two horns in the stock locations is nil.

[Miguel]

I went with the stobel myself using the normal wires They should be rated fine for 10amps.

here is a link of my install:

http://www.elisetalk.com/forums/show...498#post121498

[tvacc]

subbed

[newman]

Mounted mine to the swaybar bolts. Really straightforward. Removing the OEM horn wasn't too bad. I lossened the oil cooler like the OP did, but was able to just stick a racheting wrench in there and loosen the horn fairly quickly.

[ChrisH]

I put my Stebel Nautilus in the front air intake in order to optimize the loudness from the horn. I kept the original horn in place and operating as well. (Safety factor in case the new horn or its relay fails.)

My installation is described (with pictures) at the following link:
Stebel Nautilus 139 dB horn