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Dual Air Horns on the RT


moshe_levy

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Yesterday, I removed the tupperware for the first time, in an attempt to rectify what I saw as a problem. Essentially, at the 24k service, I had the dealer install Stebel compact air horn in place of the stock dual FIAAMs. The air horn came with a 12 vdc, 30A relay, although the instructions clearly state that the relay is not required for modern bikes. The dealer left the relay off accordingly.

 

Yet, as I work with a bunch of engineers, they sneered at these instructions and demanded that I install the relay, presumably to save my horn switch from burning out - the draw from the compressor motor can be quite high, and may cause arcing.

 

Well, I decided to use the opportunity both to venture behind the plastic for the first time, as well as to use the engineers to devise something unique.

 

So what I did was, I ordered another Stebel horn, we made a wiring harness, modified the relays with diodes on the coils, and hooked both of the air horns up. The switch now sees less of a total draw than the stock horns, and I have TWO 139 db horns mounted right where the stock ones used to be. I don't pretend that a horn is a real safety feature, but commuting on the NJ Turnpike 103 miles per day, you learn that a loud horn is sometimes a useful thing.

 

By the time we finished, it was too dark to reassemble the Tupperware, so I left it off and rode home without it. The weekend's project will be to clean up the wiring, mount the relay permanently, and address my starter's sticky Bendix while the Tupperware is still off.

 

I'm thinking of taking some pics and writing an article about it, as the whole affair is pretty straightforward, and cheap as well. On my Sportster, a single air horn cost $125 in 2004. Now on the RT, the dual system cost $70, plus the time and effort for the wiring harness. Not bad! Details to follow....

 

-MKL

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I'm looking forward to seeing pictures of how you mounted the two Stebels.

 

Mounting the relay was unnecessary. The factory wiring already has a relay under the seat for the horn. The handlebar switch was already only switching the power for the relay coil.

 

The factory harness doesn't provide very large wires for the horn. By adding the relay and presumably some larger wires from the battery to the horns, you probably are getting a little higher voltage and thus a few more db out of the horns, so it wasn't for naught.

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All-

 

Yesterday, I removed the tupperware for the first time, in an attempt to rectify what I saw as a problem. Essentially, at the 24k service, I had the dealer install Stebel compact air horn in place of the stock dual FIAAMs. The air horn came with a 12 vdc, 30A relay, although the instructions clearly state that the relay is not required for modern bikes. The dealer left the relay off accordingly.

 

Yet, as I work with a bunch of engineers, they sneered at these instructions and demanded that I install the relay, presumably to save my horn switch from burning out - the draw from the compressor motor can be quite high, and may cause arcing.

 

Well, I decided to use the opportunity both to venture behind the plastic for the first time, as well as to use the engineers to devise something unique.

 

So what I did was, I ordered another Stebel horn, we made a wiring harness, modified the relays with diodes on the coils, and hooked both of the air horns up. The switch now sees less of a total draw than the stock horns, and I have TWO 139 db horns mounted right where the stock ones used to be. I don't pretend that a horn is a real safety feature, but commuting on the NJ Turnpike 103 miles per day, you learn that a loud horn is sometimes a useful thing.

 

By the time we finished, it was too dark to reassemble the Tupperware, so I left it off and rode home without it. The weekend's project will be to clean up the wiring, mount the relay permanently, and address my starter's sticky Bendix while the Tupperware is still off.

 

I'm thinking of taking some pics and writing an article about it, as the whole affair is pretty straightforward, and cheap as well. On my Sportster, a single air horn cost $125 in 2004. Now on the RT, the dual system cost $70, plus the time and effort for the wiring harness. Not bad! Details to follow....

 

-MKL

 

Wondering about the purpose of the diodes on the relays? Diodes limit the flow of current to one direction. With a dual air horn setup, I assume in parallel, diodes seem to be unnecessary. Why did you install them, what do they do and where are they installed in the circuit?

 

Inquiring minds want to know. thumbsup.gif

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Wondering about the purpose of the diodes on the relays? Diodes limit the flow of current to one direction. With a dual air horn setup, I assume in parallel, diodes seem to be unnecessary. Why did you install them, what do they do and where are they installed in the circuit?

 

Inquiring minds want to know. thumbsup.gif

 

Scroll down to the bottom of this for a full explanation. Basically, the diodes suppress voltage kickback spikes that you can get from switching heavy current loads.

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I'm looking forward to seeing pictures of how you mounted the two Stebels.

 

Mounting the relay was unnecessary. The factory wiring already has a relay under the seat for the horn. The handlebar switch was already only switching the power for the relay coil.

 

The factory harness doesn't provide very large wires for the horn. By adding the relay and presumably some larger wires from the battery to the horns, you probably are getting a little higher voltage and thus a few more db out of the horns, so it wasn't for naught.

 

I installed one Stebel compact nautilus air horn on my Roadster, and I used the relay. I will admit that I did not know the bike had a horn relay, and I felt stupid. However, as you noted, I used heavier gauge wiring directly from the battery, so there is some benefit.

 

Now can someone explain why BMW uses a relay for the horn, which is used only occasionally, but not for the headlights, which are always on and draw a lot of current?

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Wondering about the purpose of the diodes on the relays? Diodes limit the flow of current to one direction. With a dual air horn setup, I assume in parallel, diodes seem to be unnecessary. Why did you install them, what do they do and where are they installed in the circuit?

 

Inquiring minds want to know. thumbsup.gif

 

Scroll down to the bottom of this for a full explanation. Basically, the diodes suppress voltage kickback spikes that you can get from switching heavy current loads.

 

Thanks. Interesting reading. Don't know for sure if it applies to the horn circuit since the original horn relay works w/o one.

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It's a much bigger issue when things are switched via solid state circuits than with a contact switch like the horn. However, if you pull the stock horn relay and look at the diagram on the side of it, you'll see it has a quenching diode in parallel with the coil.

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It's a much bigger issue when things are switched via solid state circuits than with a contact switch like the horn. However, if you pull the stock horn relay and look at the diagram on the side of it, you'll see it has a quenching diode in parallel with the coil.

 

I stand corrected. grin.gif

 

Which then raises the issue of the original poster who added a relay and diode when they were already in place.

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I'm having trouble finding room to mount one on my RT.

Would you mind sharing where and how your's were mounted?

 

Did you have to make up a special bracket?

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I'm having trouble finding room to mount one on my RT.

Would you mind sharing where and how your's were mounted?

 

Did you have to make up a special bracket?

 

Answered my own question in another thread.

 

Here is the answer.

 

1169243718.jpg

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Jealous. I want a Stebel on my 1100S.

 

-Eff

 

Eff - I put the compact Stebel Air horn on my 1100S without any problems. It even fits in the stock location!

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