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This posting is about completing a trouble-free Stebel installation in an Exige by using a relay and the least amount of new wiring as possible. There are many Stebel postings with lots of pictures, but those postings do not provide solutions to a quirk that seems to affect Exiges when routing new wiring across the scuttle area in the installation. :panic:

A couple of Exige owners (Doghouse and I) have experienced engine cut-out when honking the horn after installing a Stebel using a relay and (+) and (-) wires connected the Stebel to the Exige remote battery terminals. It seems the that certain wiring set-ups can cause electrical interference in the scuttle area beneath the service panels, which leads to engine cut-out. :shrug:

Credit goes to Doghouse and TheViper for helping out. I am not an electrical expert, but I solved the cut-out issue because of their tips and by using a process of elimination to isolate the problem. :up:

There have been many discussions about not needing to use a relay (see other Stebel posts), but the purpose of this post is to address using a relay in an Exige installation. Sourcing power for the relay in an Elise is a PITA, whereas it is a no-brainer in an Exige because of the remote battery posts in the scuttle area under the driver's service panel.

In this wiring, the OEM horn wires are used to activate the relay mechanism, and the Stebel uses 12 gauge power and ground wires. This wiring set-up will prevent horn wiring damage or possibly fire from the horn wires overheating, because the Stebel draws a lot more amperage than the OEM horn circuit is designed for.

Prep Tips:
- To remove the horn, use a small flathead screw driver to pry off the OEM horn connectors through the access holes in the CF. crash structure. Then pull and twist (C/W) the horn off. Use a magnetic thingie to retrieve the nut and lock washer.

- After removing the stock horn, plug the three holes in the CF crash structure using two 7/8 inch and one 5/16 black nylon hole plugs. This will help keep water out of the horn area when driving in the rain. See picture below.

Wiring:
- The OEM horn's positive wire (purple and brown) is attached to relay terminal 86, which I wired as the (+) side of the relay coil circuit. I made a wire extension to reach the Stebel.

- The OEM horn's ground wire (brown) is attached to relay terminal 85, which I wired as the (-) side of the relay coil circuit. Again, I made a wire extension to reach the Stebel and wrapped both (+) and (-) wires in wire / cable cover. See picture below.

- The Stebel's (+) terminal is wired to the Exige's (+) remote battery terminal using 12 gauge wire and a 20 amp fuse just before the terminal connection. This power wire is in a plastic cable cover that is routed through the radiator hose opening in the passenger side wheel well, up and across the scuttle area toward the driver's side, behind the brake booster and up to the (+) battery terminal. Route it around (away from) the main wiring harness. See picture below.

- The Stebel's (-) terminal is grounded to the chassis using 12 gauge wire fastened to the chassis (with a stainless steel fastener) using an existing fabrication hole drilled by the factory. This ground wire is about 8 inches long. See picture below.

Pressing the horn button cause the relay coil circuit at terminals 85 and 86 to close thereby bridging terminals 30 and 87 and sending power to the horn. :coolnana:

I was hell bent on being able to lay on the Stebel for as long as necessary, without electrical consequences, should the need ever arise. In 1996, I was at a stop-light in my new daily driver, and a jacked-up 4-wheel drive SUV ahead of me decided to change lanes and slowly backed into my car, over the bumper, onto the hood, and stopped when his tow bar was a foot away from my windshield. I was on the horn the whole time (about 10 seconds). The guy was apparently brain dead after a long day and said that he did not see my car behind him or hear its horn. :wallbang:

This scenario could easily happen in a Lotus.

Oh...this horn is LOUD!
 

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Mulholland>SCC
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When I search online (thinking of buying one) I get motorcycle horn. Is it the same?
 

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the CF crash structure
One small nit to pic and a suggest for the future.

The nit is that the CF crash structure IS NOT Carbon Fiber - it's simply black fiberglass.

The suggestion is to use a relay socket to connect the wires to the relay. Instead of individual wires being plugged into the terminals on the relay, you wires the socket, and simply plug in the rely. The one pictured below is 75 cents. But you really don't want a pre-wired one, look around a bit and you can easily find them with out the wires and with the connector pins that you crimp onto the wires and snap into the relay socket. It makes things a lot neater, and more professional - and much more reliable.

By the way, good installation of the horn. :up:
 

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Discussion Starter #4
TimMullen, thanks. I'll check out relay sockets and upgrade my relay wiring next time I am under the car. :)

agirls, yes...it is indeed the motorbicle version of the horn. -eek- The car and bike versions have the same electrics and decibel output.

The difference between the bike and car versions is in the way the horn housings are packaged and direction of the horn openings. The bike version is more compact...more importantly, the horn openings point sideways instead of forward as the car version does (and more prone to collect moisture given the low slung placement and nearby grill openings of the Exige and Elise). The sideways orientation of the horn openings does not diminish the strength of the horn sound.
 

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Sorry to dig up old thread, again, but I too have just experienced the cutout infinitely repeatably, in my Elise. Damn strange sensation, because it's so delayed.

I once accidentally wired two standard horns in series on a bike, which only allowed the first one to fire. It wasn't so much that their resistance was dropping voltage to the second, but that horns essentially act like a little controlled short on speed. So anything else on that circuit is left channeling Robin Williams before he got clean :panic: Second horn in that situation doesn't get to time its own open/shunt behavior which must be driven by the spring action of its own diaphragm.

I wonder, if the electric fuel pump is dropping out in a similar contention, thus the delayed reaction to the horn.

I'll have to tap from somewhere besides the 20A aux on fuse 1.
 

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Discussion Starter #7
When my car was experiencing the cut-out, the horn sounded immediately and the engine stumbled slightly for about 1/2 second and then recovered.
 

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Discussion Starter #9
I am not sure that there is any change in procedure.

The horn's (-) side is ground to the chassis and not the negative post of the remote battery terminal on an Exige.

The engine cut-out that my Exige experienced seemed related to the routing of the horn's (+) wire across the front scuttle area (below the service access panels) to the (+) remote battery terminal, and positioning the (+) horn wire away from any electrically powered components (ABS unit, for example) and factory wiring harnesses eliminated the engine cutting-out.
 

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So it sounds like you suspect RF or induction? I tested the cutout a bit more this morning, and can now give a little more info. At low throttle position w/low revs ~2500, the cutout does not happen. At higher revs it always happens. Cutout does not happen at all while horn is held (tried for 10 sec:wave:). But as soon as you release horn, it stumbles, always for about 1 to1.5 seconds.

I no longer suspect fuel pump or fuel pump relay. That would be more irregular.

Immobilizer? Rev Limiter? ECU? If the entire electrical system was experiencing a short, I'd expect to see the electric tach and speedo dip fast (or spike the other way). I wonder if a big capacitor or a choke between the horn and 12V would hide its transition to off from whichever component is not happy.
 

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Me too!

Sorry to dig up old thread, again, but I too have just experienced the cutout infinitely repeatably, in my Elise. Damn strange sensation, because it's so delayed.

I once accidentally wired two standard horns in series on a bike, which only allowed the first one to fire. It wasn't so much that their resistance was dropping voltage to the second, but that horns essentially act like a little controlled short on speed. So anything else on that circuit is left channeling Robin Williams before he got clean :panic: Second horn in that situation doesn't get to time its own open/shunt behavior which must be driven by the spring action of its own diaphragm.

I wonder, if the electric fuel pump is dropping out in a similar contention, thus the delayed reaction to the horn.

I'll have to tap from somewhere besides the 20A aux on fuse 1.

I just hooked up my Stebel in my 2009 Elise and connected the horn power to the aux fuse #1. I experienced engine cutout causing the car to stall. Did you figure out how to fix the problem? Does it need to be connected to another fuse #. Is it the grounding point? I grounded to my aluminum radiator using an extra bolt. since it had an easy hole to attach to. Thanks for the help!
 

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I just installed one in My Exige, and have not checked to see if the engine cuts out

On checking the wiring diagram the wire coming into the horn fuse is 1.5mm, just large enough to handle the horn load, but the wire out is 1mm, not large enough.

I bought a fuse adding widget on amazon as pictured. The original 7.5A horn fuse is on the bottom, new 20 amp with feed for Stebel horn is on the top. I have not quite got everything buttoned up to see if the fuse adder will hit the access panel, but worst case I will have to remove one of the two spacers from under the fusebox

Now to check and see if the engine cuts out......

my guess is that the engine cut out is actually alternator cutout, the sudden release of an inductive load causing the alternator to get out of voltage spec for a fraction of a second. Giving it such good contact to the battery[and voltage sense] being the difference in the Exige.
 

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"my guess is that the engine cut out is actually alternator cutout, the sudden release of an inductive load causing the alternator to get out of voltage spec for a fraction of a second. Giving it such good contact to the battery being the difference in the Exige."


I agree that it is likely an alternator cutout. Thanks for the help. How did your add-a-fuse work in your installation?


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Haven't actually driven it, but started it and no cutout at idle or 3k rpm. So far so good.

Got waylaid the last few days, have to button up the front clam to make sure the add a fuse fits under the cover, but I think it will
 

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Did some troubleshooting today, and finally figured it out. It turns out that it was a poor quality relay that was part of a wiring harness that I bought from Amazon. It was a piece of crap made in China. This is what was causing the engine to cut out. I did some troubleshooting by disconnecting wires and everything pointed to the actual relay. When I replaced the relay with the one from the Stebel horn, it stopped cutting out. There must've been some type of voltage spike when I let go of the horn button which caused the engine to cut out like that. Finally, success!!...

And a very LOUD horn!!!


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