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Hook double horn to separate or single relay

ron2k_1

Dec 17, 2014
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Hi guys,

Need help. Bought this air horn set for my motorcycle.
https://www.amazon.com/SEGER-Trumpet-Car-Horn-Set/dp/B07PDF7GTL

I also made the attached wiring diagram using just one relay to power both horns with one line.

My question is whether I should consider using 2 separate positive lines from the bike battery with separate fuse and relays to each horn instead. I will then splice the original horn wires to act as the triggers to both relays simultaneously. How would you do it?

Thanks,

Ron
 

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Bluejets

Oct 5, 2014
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My question is whether I should consider using 2 separate positive lines from the bike battery with separate fuse and relays to each horn instead

If the one relay has sufficient current rating, the original would suffice.
How much current is involved to each horn?
Length of run and cable size may come into consideration also whether or not the battery can handle the load.

One thing to note is you do not supply the original wiring diagram and it is highly possible the horn would be operated via earth return in which case you new wiring control might need to be modified.
 

Martaine2005

May 12, 2015
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One thing to note is you do not supply the original wiring diagram and it is highly possible the horn would be operated via earth return in which case you new wiring control might need to be modified.
@Bluejets makes a very good point.

Edit: posted an image but lost it:rolleyes: I will post it later

Martin
 

dave9

Mar 5, 2017
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If the horns are unreliable, subject to shorting out, then you could run two fuses, fast blow and lower current than the one right after the battery, to each of the horns between it and the single relay, so the failure of one horn does not blow a single fuse to both. Note that in this case fuse tolerance is important to ensure the fuses to each horn blow first, which means you should choose a major brand fuse. Generic fuses are often nowhere near their ratings, you can almost count on them passing much more current before blowing.

If the horns are reliable, and the pair draw less than 30A, you should only need one relay since 30A size is not uncommon in automotive, but i would use a new stock (from a high volume/turnover merchant) major brand relay for reliability. If using lower quality or old relays, then the redundancy of two would again safeguard against the failure of either.

There is no need to make two separate runs from the battery. This is within a reasonable wire size, perhaps 10AWG, or higher (smaller wire) if you find specs for these horns to determine true current.

Keep in mind that if your horns are too loud, it can incite road rage which is something you don't want to be a part of on a motorcycle.
 

Audioguru

Sep 24, 2016
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They are not "air" horns. Instead they are ordinary electromagnetic car horns.
 

Bluejets

Oct 5, 2014
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Only negative I can see are the trumpet type are not normally used on motorcycles as they can quite easily be damaged due to water entering the front with no way out. Rust hell out of the diaphragm, makes the horn sound like s frog under water.

Some have tried placing the trumpet face downwards but the water still finds it's way in.

The disc type commonly used are normally drained.
 

ron2k_1

Dec 17, 2014
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One thing to note is you do not supply the original wiring diagram and it is highly possible the horn would be operated via earth return in which case you new wiring control might need to be modified.

I have absolutely no idea about what you just said. As expected the manufacturer didn't offer any wiring instructions. I'm a motorcycle enthusiast with basic knowledge of relays and fused power etc. They are plug and play vehicle horns (just twice the noise), so I'm assuming 30A safety is plenty. Also I found out that one horn is low pitch and the other is high pitch so both need to be used in conjunction and together.

If you guys can describe what I need to modify on my writing drawing in the first post with words for dumb people, that can help.

Thanks
 

Bluejets

Oct 5, 2014
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If you guys can describe what I need to modify on my writing drawing in the first post with words for dumb people, that can help.

In all fairness you did not quote your "dumb ass rating" in the original post.:confused:

Many automotive systems (including motorcycles) use "earth return" wiring systems.
In these the battery power is connected directly to a particular device and the device is operated by a switch or button in the return or earth or negative lead.
Reason being it saves extra wiring which can lead to voltage drop at low levels such as in 12v systems.
Adding wrongly configured devices can and do lead to "feedback" in the system which can and does have rather strange outcomes.

It may be that your original wiring may need to be modified to suit the new horns.
I say maybe as we have no idea what your motorcycle wiring diagram is like nor do we have any idea what the specs on the horn are to be able to adapt.

Simplest might be, as you have everything at your fingertips, is the tried and proven, suck it and see principle.
 

Kiwi

Jan 28, 2013
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The way you have shown it in your diagram is perfect. No need to overcomplicate it.
 
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