i've got a problem with the wipers on my 2002 galaxy that i hope sombody can help me with please sorry to post in here, but there is no galaxy specific forum

luckily i have discovered it today when i went to wash/wipe, and not later on when it is raining and i'm on the motorway or something

when you switch the wipers on, they kind of 'twitch' but do not sweep across. i am presuming that as they twitch they must have power and must be getting a CAN message, so what can it be? i have lifted them off the screen and they are not stuck or anything. any known faults?