Monday, March 21, 2011 - 08:59 am, by: Tom Richards(Tomr)
the sensor is a magnet in side a "cork' Th ecork fits over a shaft and moves up and down depending on the level. The cork may be stuck or water logged.
remove the sensor, it turns anti clockwise and have a look. ( use a set of long nosed pliers in the 2 locating holes to turn it)( unplug the lect lead before turning it) clean the shaft with metho so the float doesnt stick.