What's the brown/white wire do?

So I'm looking for a place in my headlamp bucket to connect some heated grips for my '79 KZ750.

There's a brown/white wire in there with nothing connected to it and it seems to be providing 12V.

I was planning on snipping the line to the headlamp and patching in there, but if this wire is producing 12V, I'm not sure I need to.

But then what's this wire doing just hanging out with nothing to do?

My eventual plan is to replace my fuse holder with a blade style holder with 4 fuses and use the fourth fuse as an extra circuit with a switched relay for accessories like this. But for now I just want my grips working.

Here's the wire I'm talking about:



And you can view the whole wiring diagram in the file base:
www.kzrider.com/filebase/doc_download/284-z750b4

Would go with the brown/white wire for positive and the black/yellow wire for ground.

Good Fortune!

Kawasaki probably uses this harness in several motorcycles, so consider it a free be if it has 12 volts(switched I hope) for your heated grips.

That is 12v coming through the 10A fuse for tail, front-marker, and gauge lighting.
Adding up the watts: tail/markers = 3 x 8w, gauge lights = 4 x 3.4w.
That's about 38 watts of lighting. That's roughly 3 to 4 amps.

You might be able to get a few amps from there before the fuse blows.
If your gloves are about 40 watts total, you might be ok, assuming all of the wiring is good etc.
50 watts may be pushing it.

If the wiring is dirty, and causes the resistance to be a bit higher, you might get away with a higher wattage set of gloves.

The ground to use is shown 4 wires to the right in your post.

Ok, thanks guys. Looks like I'm good to go.

And yes thankfully the brown/white wire is switched so I don't have to worry about leaving the grips on and draining my battery.

Your accessory gloves or whatever should say in the inclosed literature how much current they draw.
Before switching them on, I would check the voltage at the battery, then at the accessory Br/Wh connection. See if there is much of a drop, that will tell you if you have resistance along the circuit already. If pretty close, then turn on your gloves and double check the voltages again.
Also If you use your DVOM set to the 10amp scale, you can first Measure the current load of your Gloves separate to anything else, and then measure across the 10amp Tail Light fuse. See what the Factory current is pulling, and what your gloves are. Add them, like Loudhvx said. Look at the total.
If to high, you may want to use the Br/Wh to just latch a relay, and run a separate power feed circuit from the battery, with a fuse of course. This would take the additional load out of your old wiring and switches.

The brown/white wire is connected to the blue wire circuit in the turn signals. The blue wire provides power for the 'always on' filiment of the light bulb in the turn signals, the other wires to the left & right (green and gray, respectively)provide the flashing power when they are activated. The brown/white wire is likely there for the UK version of this bike, which uses a 'city light' in the headlight bucket which is a low power (about 4w) bulb. The entire circuit this wire is on only handles 10 amps. It is unlikely this circuit, or the existing wiring harness, for that matter, could handle the load of electric heaters - I would proceed with caution. In fact, the entire alternator system is not really designed to generate more than about 20 amps, be careful not to overload your entire bike!