leclkada

Hi all my car is a y reg ford galaxy 1.9 TD Ghia (115ps)i need a little help with my parking sensors they just dont work at all no noise nothing i have only just got the car and in general its the best thing since sliced bread i have pressed the button in the front question is it supposed to click on or off like the hazared switch question 2 where do i start to look to find out where the problem is step by step if poss guys as i have not got a book yet