hi, mine just did the same, and it failed its mot too because of this, it will be the wiper ittermitent relay, open glove box, unclip the bar on left hand side that smoothly lowers the glove box, pull glove box fully open by pushing in rubbers that stop it, unscrew the two small nuts secureing fuse box, push clips together and push fuse box in, check your focus manuel, you will need to go to your local ford garage, ask for the parts department, tell them you want the intermitant wiper relay, couple of pound, there is two in fuse box, one for front one for back wipers, they are both the same, the front one is the one on the right hand side, in your manuel its on page 142, its relay r19 mate
linden fisher, June 2010