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B25 horn
#814010 06/26/20 1:23 am
Joined: Jul 2013
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JoejBSA Offline OP
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Hello all,

Have a 1967 B25 that I recently acquired got a new horn/dipper switch and wired it up , However you can honk the horn when the bike is off and even when the key is removed , I’m assuming that pushing the button completes the circuit to make the horn do its thing , BUT will this drain my battery or is it wrong?? Or is this normal for this age and model?


Thanks
Joe

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Re: B25 horn
JoejBSA #814035 06/26/20 4:07 am
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Well, it is wrong.

But thinking about why hurts my brains, so you need to to some wire tracing, per the manuals...

Bet you'll figure it out.

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Re: B25 horn
JoejBSA #814039 06/26/20 6:16 am
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Sounds like the horn takes its feed before the switch. The wiring for my A65 is shown that the lights are wired before the switch, so any good walking by can play with your bike and flatten the battery. However if no one is playing with your horn (ooh er) then it won’t drain your battery as it’s not in circuit until the button is pressed.


HTH

Last edited by Allan G; 06/26/20 12:13 pm.

Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: B25 horn
JoejBSA #814042 06/26/20 6:31 am
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Well my B44 (B25 with bigger bore and stroke) has been that way since it left the factory and no one has ever pressed the horn to flatten the battery. I prefer it that way, if you are parked on the side of the road and have just sat on the bike before turning the ignition on and you see a potential accident developing you can just press the horn button.

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Re: B25 horn
JoejBSA #814045 06/26/20 7:01 am
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its normal .
the horn is designed to work without a key . .. always at the ready .
so it is normal and correct ... ( for stock wiring ) ... for most 60s britbikes .
it's how it was done back then as a safety feature . ..
the load is way too much for any Lucas key switch .
and bsa/triumph didnt run relays for single horns .

the ..Rupert's ratio.. wiring diagrams for ... B25 /B44 ... 67
show
brown/blue wire ... from batt. neg. to horn
brw/blk wire ... from horn to horn-button ... button is a momentary-contact to ground
battery has a fuse to ground on positive side

a lead acid battery drains about 5% per month all on its own .
and any drain from the horn only happens
when the horn button is pushed and the horn circuit is completed .

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Re: B25 horn
JoejBSA #814062 06/26/20 12:16 pm
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I don't press the horn on my Lightning often so I am not sure on this, Unless you have the Twin Horn setup then they aren't particually audible from a car.

I beleive however that the Horn wiring passes through the switch on the OIF bikes (or those that use that kind of switch system)

I think if the horn was stuck on then you might stuff up the switch but its like using a 6v horn on a 12v system, its not ideal but it will work without causing long term damage.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: B25 horn
JoejBSA #814065 06/26/20 12:27 pm
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Yeah, my B44 was originally wired that way and the horn would go off at entirely random times. When I say random, what I meant was, the most inconvenient and embarrassing times. Luckily the horn had the tone and volume of a partly strangled duck plus my nearest neighbors are more than 20 yards away, so no one was disturbed in the early hours of the morning.
When I rewired the bike I fed the new horn and button through the ignition switch, no problems so far.

Re: B25 horn
Dave Martin #814087 06/26/20 5:03 pm
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heres , I think , a 69 wiring diagram .
the lighting switch has changed .
Optional turn signal are added
fuse is moved to negitive side ... and horn wiring Remains the Same as 1967 ... its wired hot to the battery .
triumph wired the horn very similarly ... except Triumph horns were wired to even bypass the fuse .
no fuse and no key improve the reliability of the horn ( Lucas logic )
if you want to improve on the original
i wouldn't run the horn throught the ignition switch ... without a relay .
There's a decent chance the horns draw
will act as a kill switch , when run through the limited ampacity of the switch .
[Linked Image from i.postimg.cc]

Last edited by quinten; 06/26/20 5:06 pm.
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Re: B25 horn
JoejBSA #814151 06/27/20 2:05 am
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Thank you all for the quick responses and excellent info from you guys that have these , thanks again!


Moderated by  Allan G, Jon W. Whitley 

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