FOAK: Kawasaki brake / tail light electrics

Hi all,

I was hoping that someone could explain the tail light / brake light
electrics on my Kawasaki ER6-f to me please.

I've recently fitted a givi top box, and the light on the box comes on
when the tail light is on, but goes off when I activate either of the
brakes (front or back). Looking into it further, I found that the
brake light is a single bulb with 2 filaments. When in normal running
mode, the tail light filament is lit. When I activate a brake pedal,
that goes out and the brake filament lights up.

The Givi top box light kit has these weird connector things that
splice into the existing brake light / tail light cables. After
splicing in, I see that I have 12v at the Givi box connector during
normal operation (tail light lit), but that drops to 0v when I
activate a brake lever.

Can anyone explain to me how this dual filament light works ? Are
there multiple cores in the single cable going to the light fitting ?
If so, how does this work?

My end goal is to have the top box light off unless I am braking, and
then come on. This seems a safer bet than having it go off when I
brake and people getting confused and running into the back of me.

Thanks,

 

Sounds to me like you need to run an earth wire to it. but ICBW.

 

Yes, that's kind of how they work. In some applications, both light up,
but in some, only one does.

That suggests you either spliced it into the rear light + ground circuit
or in the rear light + brake light circuit. As the rear light goes out
when you activate the brake, I would guess it's the former.

You should have three connectors at the brake light unless they're doing
something really weird. "Use the other one" .

 

It looks as if you have connected to the stop and tail circuits insted
of stop and earth. When you switch the lights on the the the light on
the box would be earthing through stop light on the bike, is it glowing?
When you operate the brake, the potential difference on both sides of
the bulb would be the same 12v, which why you get 0v when the stoplight
is on you need to check the wiring you have fitted and find the
stoplight and earth wires You could trace them back from the stop and
tail ligt on the bike.

 

Hmm - I thought that if there were three wires in total, it would be
live, neutral and earth. Is this not the case? There was no mention of
earth in the Givi instructions, and the givi cable only has 2 cores -
again, this looked like live and neutral to me.

I always thought you needed at least a live and a neutral to complete
the circuit. What have I missed ?

The unused wire is earth. But if I add this in, I'm dropping neutral
or live. Will that still provide a complete circuit ?

Thanks,

 

Missing earth.

 

There is no neutral or live on a bike - you're dealing with a very
simple DC system, which has only two connections. Live (+ on the
battery) and ground (- on the battery).

No, one of them goes against ground/- and the other one is spliced into
the circuit that you want to use to trigger the light.

Nothing. You're assuming the presence of one more phase because you're
thinking household-type AC wiring.

That's the whole point - you determine which of the two wires you've
spliced into goes 12V when you trigger the brake, splice on of the two
connections in and put the other one against ground. Voila, you've got a
circuit.

 

You don't know very much about about auto electrics, do you?

Not outside of A/C domestic wiring systems, no.

What would be the difference between neutral and earth in this system
of yours?

What would be the difference between neutral and earth in this system
of yours?

 

No, and this is really easy.

one wire will be a common -ve
one wire will be +ve for the light.
one wire will be +ve for the brake.

If you look at the connector on the back of the bulb it should be
possible to work out which wire each is.

 

I thought I would but I've been rather preoccupied by other life forms.

 

So, I'm not missing anything besides a complete lack of comprehension
of the problem domain. Now that you've pointed that out, far more
kindly than I deserved, I've read some things and now have a FAR
better understanding of the setup. Thanks a lot!

Genius, thanks - I shall rectify my screwup tomorrow.

 

5 minutes outside this morning and it now runs as expected - brake
comes on, brake light comes on

Thanks again!

 

i don't get it.