Originally Posted by
Swedish Steve
Each tank has a water sensor. This works by sending a signal down through the fuel which is reflected off the tank bottom surface. The time the signal takes to make the journey is measured. If there is water or ice in the tank the signal will be reflected from the fuel/water (or ice) interface. The resultant shorter signal journey will trigger the water in fuel maint message. So yes the water sensing system will react to ice as well as water.
Am I right in assuming that this detection method will only work when there is a distinct boundary condition - ie a layer of water or ice with a layer of fuel on top - as opposed to the situation where the tank just contains a mixed fluid?