front wipers on renault scenic are possed?

hi there i have renault scenic (2000 model) front wipers seem to have a mind of there own when on intermitten they stop any were randomly on the screen or they run on for a few minutes after being switch of also they stop on 1st and 2nd speed have replaced wiper motor replaced relay but to no aviel (second hand) problem still there but car refused to start been told relay is programmed to car this seems to be a common fault on scenics as i have googled the problem and not only one with this fault so would be gratfull for any help to be pointed in right direction