Problem with warning lamp
 

I have Passat Variant 1998.And yellow warning lamp indicating that there is no water for washing the windscreen is on,although it is filled.I emptied the ,,bottle,, and filled it once again,too see will it help,but no result.Is there any way that I can solve this one,it`s obviously that float(the thing that ,,knows,, how much water there is,don`t know how to say that in english) is broken or something...

Thanks in advance,Marko