I had same trouble with my head light washers and screen washers would only give me a litte water I found out the washer bottle inlet rubber was blocked wat to do remove offside wheel and undo the wheel arch screws and pull to one side you will see the washer bottle there are 2 rubbers. the top one is for the headlight washers and the bottom one is for the screen washers you can pull the rubbers out and you find the rubbers are like a fitter . clean them or air blow them out then put a water hose pipe in the bottom of the washer bottle and make sure flush the the bottle well then refit make sure you put the top rubber and sensor in right it should opean up for full and down for low on water then test with water you find when you fill with water the low water light will not go out till you switch engine off for a second time and it will reset hope that helps you good look