either the sensor float is full of water
or the wires are broken. Easy to test, pull the plug off the sensor, bridge with a wire and light should be off. If not, wire broken.
In case that is o.k., pull the sensor out, usually the float is full of water because of corrosion of the contacts or the contacts are corroded.Shogun E32 Tech Tips: http://twrite.org/shogunnew/topmenu.html