Seems to be a bit of mis-information on here about this, lets see if I can add to it
1. Headlight and window washers use the same bottles, however there are 2 bottles at the front of the Zed, linked by a pipe so that when you fill the main one, it balances out with the other
2. Headlight washer will only fire up when you have dipped/main beam on, engine running and use the wash window stalk or button on the dash
3. Headlight washer will only work if the levels in the bottles is high enough. At a certain level only the window wash will fire and not the headlights.
4. The button is to manually activate the wash. Its not a toggle on/off (certainly in my old MY2003), it fires when you press it.
5. Once the washer has fired with the window washer, it will only fire on something like the 5th wash of the window, not every time.
And yes, if you want to see it work, clean and dry the car then fire it, it loves to cover a clean car in spray!