Interestingly I am also having the same problem with my Dynamique DCi 120 2003. When I first got the car the auto wipers worked perfectly fine, but now they only work for one wipe when I move the stalk or turn the mechanism on the end of the stalk - this basically means that the auto wipers are not auto wiping!

(this is just one of many problems with my Megane).
The auto lights do actually still work though (boy, it feels gooood to say something positive about the car), and so from reading the posts on this subject I am thinking that the problem must not lie with the sensor but somewhere else

?? I have also just acquired a new fault on my megane (ooo the excitement), where I turn the rear washer on and the wash comes out on the front windscreen instead...but the rear wiper still cleverly knows it needs to wipe, even with no wash!!

Any ideas???
I'm wondering if my electrical problems may have the same cause. In addition to the above, the passenger side window isn't working at all (tried resetting), the boot pops open randomly when I'm driving, and the lights on the dashboard/radio/clock sometimes just turn off briefly (I'm hoping that the brakes and power steering aren't affected when this happens, as it looks like an electronic failure). Any help or advice that could be offered are much appreciated!
I'm not sure why I have still got the car...well I do - I love driving it, and without allllll the electrical problems I have had, there is a good car in there somewhere!