Do I need a horn relay with this horn?

[jabberwoky]

http://www.partsamerica.com/ProductDetail.aspx?categorycode=3074&mfrcode=WLO&mfrpartnumber=3102T

Bought this horn, will I need to use a relay or can I just plug it in?

[Chilly Willy]

Plug it in and let us know what happens!   Where's your sense of adventure? 

Seriously, check and repost your link--it leads us to a check-out form.

Chilly Willy

[domas]

I bought 2 aftermarket electric horns. They came with relay. It is realy neat thingie. First of all if the horn is more powerfull than stock, it can draw too much power and blow the fuse. I made a separate line from the battery with separate 20A fuse.

Relay has 4 contacts. One for cable from battery, one goes to horns and two are for old horn connections. When old horn should sound, it switches on the relay instead, which activates the big horns.

I'm really satisfied with the results. Car drivers definately hear me now.

So my answer would be find out what max current your new horn can draw and if it is not too high plug it in the old connection. If it is a big one or if you are unsure about the current draw, use the relay. You dont want to be stranded on the side of highway after pressing the horn button

[sledge]

You need to consider the horn switch, the contacts cant handle huge amounts of current, they will burn up or in the worse case scenario weld together. The wiring may not be able to handle the extra current without overheating. I wouldnt chance it, fit a relay.

[Wrecent_Wryder]

A3

[The Buddha]

OK forget those guys ... nothing in the wiring handles as much current as the damn headlight and people run 100's ... 10 amps almost ... you're using a piddly 5 max at that horn ... run it, no problem. On vulcan's and eliminators I have run 2 of them and still worked out OK. That thing is nothing compared to your headlight.
Cool.
Srinath.

[Wrecent_Wryder]

[4

[jabberwoky]

pluged it in, works fine.  I just have to make a mount for it.  I am just afraid of frying the switch.  It is a '06 gs500f in case in matters.

[Jughead]

It won't fry it unless you hold it down for 30 Minutes at a time.Everything will be Just fine.

[sledge]

The difference between horn and lighting circuits is time, horn operation is occasional and momentery, lighting operation is lengthy and constant. The horn switch-contacts are the weak point and there is more to it than just the horn current. Back EMF or voltage-spikes caused when the coil in the horn de-energises is what will kill it, you will get a bigger spark across the contacts when you let go of the switch than when you first press it, similar principle applies to ignition coils. It doesnt happen in lighting circuits as there are no coils there.........time will tell.

[The Buddha]

OK as someone who has opened their first horn switch assy 8 years ago ... the horn and starter are the same damn switch. Nothing frail about it. Its got one copper head about the size of a peppercorn hitting another about that same size. The wires to it are the same as the headlight.
Cool.
Srinath.

[CO_GS500]

Ah, seshadri_srinath, but the starter has relay.

jabberwoky, not sure what the best path forward is for you, consider:
1) play it safe and add the easy to do relay
2) research the norm limits for the wiring and switch that exist for the horn circuit
3) measure the current draw on the stock horn, somehow determine the same for the new horn, and use/don't use a relay depending on what you find. 

Easiest solution sounds like just tossing in the relay and calling it done.

My Haynes manual does not reveal the current draw of the stock horn, please let us know if you find that out.

[CO_GS500]

More....FWIW:

I just tested the current draw on my GS's stock horn as explained here: http://www.chip.com/buick/techtips/hornrepair.html and got just a hair under 2amps.  The horn did not sound during the test  but worked when I put it back on the bike.

[Wrecent_Wryder]

[3

[sledge]

The fact the horn DIDNT work during the test suggests to me that your charger cant deliver ENOUGH current (or Amps) to power it. The output current will be regulated depending on the size of the transformer to prevent it becoming overloaded and burning-out. I guess yours is too small to power the horn. Try a bigger charger. If its not sounding, its not working and if its not working its not drawing full load current. 18 amp @ 12v dc will generate a pretty fearsome and destructive arc. Notice that in the test procedure it says if you touch the terminals they will become pitted........that is exactly what will happen to your horn-switch contacts if they cant handle the current.

Time to consult Starwalt for a 2nd opinion I think.

[CO_GS500]

Good info Sledge, thanks.  FWIW I had the charger set to 10A Charge (vs 2A Charge or 60A "Start").  I'm just glad I didn't destroy anything in the process.  That I know of.

I'll leave it be for now but will definitely go the Relay route when I add that 125-132Db horn.

What would you recommend by way of wire gauge for the battery part of the circuit, and are you a fan of using a 20A fuse or would a smaller (15A?) be safer?  Guess it all depends on the horn's secret current draw spec....

Galen

[CirclesCenter]

It won't fry it unless you hold it down for 30 Minutes at a time.Everything will be Just fine.

Which means on my commute I would fry it.

(I need a horn that stays on, or a throttle lock to I can  , ride and honk at the same time!)

[starwalt]

...What would you recommend by way of wire gauge for the battery part of the circuit, and are you a fan of using a 20A fuse or would a smaller (15A?) be safer?  Guess it all depends on the horn's secret current draw spec....

You answered your own question! Size the wire according to the maximum current of the device. It is not so secret that you cannot find out. Get a car battery, some large gator clips, and an amp meter that reads to around 20ADC. The WOLO site doesn't specify the current and says to just install the honker with the stock wires of the car. Another experiment would be to measure the current draw of a stock car horn to get a rough estimate.

Referring to your previous test, you should measure the current of the horn when it "toots" then you really know the draw on the system. A quick glance at the size of the wire going to the horn indicates a fairly low draw.  BTW I measured the current on my GS while honking -- about 1.5ADC. It drops if you muffle the horn (it was dam loud here in the digital garage!).

Why didn't your honker honk when tested? I could have been something other than pure DC. You would have to scope the output to be sure.

I suspect your charger may not have been a constant current device. The setting is probably a current limit that would be achieved after some delay.  This opinion is subject to exception of course.

As far as using a relay...just use the two wires from the original horn to actuate a relay for the big honker. Run a fused, properly sized wire from the battery to one contact of the relay and then to the honker. Leave the honker and find a suitable return (earth, ground, etc) and you should be good to go.

(Coming full circle now and preparing to dismount...) If your car honker wires are the same size as the GS wires....just use the stock wires of the GS!  Jughead had a good point. You don't plan on staying on the horn for more than a few seconds -- unless that section of your GS is between a tree trunk. 

[CO_GS500]

Thanks Starwalt!  I muffled it for my charger-test, but nary a grunt came forth.  Anyway, it's soon to be history.