my 2013 focus titanium x has oem xenon headlamps so has headlamp washers. can anyone tell me how and when they operate.. do they operate everytime you use windscreen wipers? as iv read somewhere that they only operate every now and then.  i think iv only ever noticed screenwash residue on a couple of occasions. 

They only wash the lights when the lights are on and not everytime you wash the window, to save fluid.

I'm not sure what the exact algorithm is.

Lights have to be on, and then it's every 3 pulls of the stalk...on Mk2.  I doubt they changed it for Mk3 though.

thanks guys.   ill test it out tomorrow to make sure they are working.   or perhaps best they dont in all honesty

On my mk3 they worked on the first pull after starting the engine and then every 5th pull.

They will always work the first time after you switch on the ignition, so the easiest way to test is switch on ignition, put the lights on, then operate the washers. Note that the lights must actually be on. If you have them on auto and its not dark enough for the lights to be on then the headlamp washers won't come on.