Carista allows you to lengthen the time you need to pull the screen washer stalk to fire the headlight washers. Maximum is 2.5 seconds, which is what I set mine to. You also have the option to change the number of screen wash pulls between headlight washes. I set mine to every pull so that the headlight washers are available, without any confusion, for checking, or MOT. 2.5 seconds is a long time, so easy to avoid setting the headlight washers of in normal screen wash usage.