Hi there around 4 months ago the radiator light came on under the rev counter, when i checked it the water level was low so i topped it up and everything has been fine since UNTIL driving back from work today and on it comes again but the level is fine, i no these work with a magnet inside the bottle which the sensor uses to determine the water level, i have emptied the bottle and gave it a good shack up to see if it had become stuck but everything is fine? also disconnected sensor and cleaned, even taken battery off and reconected and still the little yellow light is on. anyone have any ideas on this one would be greatfull of the help. Jase...