Motorcycle horn won t blow

[Colas LeGrippa]

Hi buddies,


I swapped the original horn on my HD motorcycle for 2 china made plastic ones (hi and low pitch)  nothing else being available here but truck flutes, and it seems they are pulling too much current because even with the battery charged at 100%, ( 12,7V), they don t work.
The engine must be running for them to horn and even then sometimes they stay muted.
I hooked up a 2,200 uF in the horn circuit with no result.
Any idea ?

[ShoemanGB]

Check the ground.  Do they ground through the mounting bolt?  I know it sounds unlikely to be the issue but it's always one to rule out. 

[Colas LeGrippa]

The gnd is the first thing I checked. I get .5 OHM
from the gnd connection point to the battery, acceptable. I am pretty sure I can connect a small circuit to boost up the voltage of the horns. It is very frustrating to be stuck behind a car at a green light because the driver is texting...🤣🤣🤣

[acheld]

Would you mind sharing which horns you purchased?   It would be fun to look at the circuit.

I can't imagine they would draw so much current that they don't work ...  though just because I can't imagine it does not make it impossible. 

[Colas LeGrippa]

The circuit is not included with the horn.
The horns are intendef to be use in a car with battery around 500 CCA so with plenty of juce, not on a motorcycle

[sluckey]

The circuit is not included with the horn.
The horns are intendef to be use in a car with battery around 500 CCA so with plenty of juce, not on a motorcycle

So, connect the horns to a car battery. Do they work?

[PRR]

Simple horns can be 5A even 10A. They need to be LOUD like a 500 Watt amp. They are crude and not optimized for efficiency since you shouldn't lean on them all day.

10 Amps in your apparent 0.5 Ohm ground return is a 5 Volt loss, leaving only 7V for the horn. And there is a minimum voltage/current to move the diaphragm enough to break the contact; 7V may be on the edge at best.

They aren't all the same. Some are just crap.

You can't f***-around with these things. Get your power done right. Use a horn made for a bike battery.

Amazon is showing me a lot of cycle horns in-stock at $9 and up and up. (However these claim 1.5A so may be lame jokes.)

If you fitted a strong battery, a junk-yard XXX automotive salvage shop would be good. Try before you buy.

[Colas LeGrippa]

Good .......then I will move the gnd rigjht onto the battery and see what happens. I ll hook up.my multimeter in series with the horn circuit to.verify how many amps the two horns are pulling and check the  voltage at the horns while the horn button is.on.  Many tests I shouldhave performed b4 posting this.
Thanks amigos😀😀😀

[ShoemanGB]

"Many tests I shouldhave performed b4 posting this"
No worries.  I can't tell you how many times at work (auto collision repair) I have to help diagnose why a horn or light no longer works after we repair or re-assemble the front end of a vehicle and it turns out to be a re-used rusty ground bolt, or fresh paint where the bolt goes, or something like horns or lights have to be in series and not parallel.  Bike charging systems are typically minimal at best, and the older the worse they are.  My old '70's bikes had barely enough for the sealed beam lights of the day and the horns, well, I could yell louder.  But my pipes usually made up for it, especially on the RD Yamaha's :-)

[Colas LeGrippa]

I owned a Yamaha RD 350 in the 70's, faster than a Honda 450, 6 speed transmission, liked it a lot. On my Harley Davidson, I soldered a big copper wire to a big copper washer that I screwed right onto the battery negative cable .
Even though, I get a resistance reading of .3 ohm between the battery and the end of the cable...tomorrow I ll perform a carbon pile battery test and dpuble check the  connections  right onto the battery posts.
Colas

[Colas LeGrippa]

Yes Sluckey, the two horns are blowing like hell when connected to my car battery

[acheld]

the two horns are blowing like hell when connected to my car battery

So THAT'S what that sound was . . .  Damn, that was loud!   

[DummyLoad]

Add a small solenoid. The current handling capacity of the switch is probably the issue. Easy enough to test out of the bike.


--pete

[Colas LeGrippa]

Very good idea Pete, thanks. I think I get it now but giving the switch a help would surely help the circuit. Would you mind drawing a simple circuit with a solenoïd ? I m not an expert with these thanks .


I did remove the horns gnd connection at the frame and replaced it by a copper wire soldered to the horns, the other end being soldered to a big copper washer bolted with the battery negative
cable to the bike frame. In doing so, I lowered the gnd resistance from the horns to the battery to .1 ohm . Both horns are pulling  8 A so the voltage drop is .8V . The alternator supplies  14V to the battery  so there is aprox.13 V left for the horns which is just fine.
So better get out of my way if not you'll get a shot of 120db high pitch sound in your ears...

[DummyLoad]

Can't really be for certain about anything without asking a question: Does the horn switch apply battery (+) to the horn, or is the switch grounding the horn? If the latter (most likely) then the attached schema should work. For the record, it would be nice to have a look at the schematic of your bike BEFORE attempting this.

For making connections to the the relay below, the connections are crimp type 6.35mm (.25inch) insulated fast-on connectors, or try to find the 3 wire harness with the molded male connector and flying leads - May be available as service part; try looking through the Doorman Catalog. Use 16AWG wire and be sure to add an inline fuse, start with 10A, if that pops, move up to a 15A.

https://www.amazon.com/Standard-Motor-Products-HR159T-Relay/dp/B0052XJ43Y/ref=sr_1_3?keywords=Horn+Relay&qid=1663645424&sr=8-3

--Pete

[Colas LeGrippa]

Best regards 😀😀😀😀

[Colas LeGrippa]

Thanks for putting me on the right track

[Colas LeGrippa]

I learned that the post no. 87a is for normally close application and no. 87 for normally open, like  I needed. The first relay I bought had only the 87a post. I hadt to  buy a 5 pin relay which has both 87 and 87a posts, the 87 a being left unplugged for my purpose.
Believe it or not, it was my very first circuit using a relay. The one I found cost me 4 bucks CAN at the electronic depot store while the guy at the auto parts was asking me 30$......plus 4.50$ taxes...
I am soldering ALL the connections, to the relay and the horns. My HD motorcycle is too shaky to use crimped connectors, so I take the time
to do it right. A faulty horn can cause death,  to the very limit, and cause my  blood pressure to raise dangerously when stuck behind a stupid car driver stopped at a green light while texting...

[ShoemanGB]

Nice.  Now that you've mastered relay's you can add big Hella lights to all your vehicles for fun and that cool retro look that was not yet retro when I first wired up a relay.