HiCustomerthis is lostrider, here is a diagram of the fuel/water separator, the concern your having is probly due to the sensor is sludged up, you can replace that sensor and clean the separator, the sensor can be purchased at your local Ford dealer, it comes with instructions on how to replace, but you will also have to have a can of brake cleaner to clean the separator, all you do is remove the sensor per the instruction sheet, remove the drain plug, take the brake cleaner and spray into the hole for the sensor and then into the drain hole, use the whole can to make sure you have all the sludge out, then reinstall the sensor per the instructions and then the drain plug, hope this helps.
That is the connector for the sensor.
How many plugs are plugged into your water/fuel separator 2 or 3?
Is this red plug part of the harness for the sensor?
Thank you for the reply, That picture is from an 2004, on the 2005 and up models they changed the manifold for the separator, the new manifold only uses the Water sensor and the fuel pump power connector, someone has changed the manifold for the separator on your truck and didn't replace the harness, its not gonna hurt anything, here is a diagram of the newer manifold assembly, you can see where the left sensor is gone now.