Water Pump is always running
The pump operates of a pressure switch to shut off (when in automatic). Look at owners manaul for schematic or remove all power and find switch by hand over hand method. Sometimes a little mechanical agitation will help relieve a soleniod or stuck spring in the pressure switch. The line to the pressure switch may have a clog and in which case could be removed by venting the line. The problem could be your FW tank is empty or low and not enough water available to prime the pump for the pump to build up to shut off head (pressure).
99 Expedition 5.4L, 3.73,with factory toe package pulling 2703 Layton (GVW-full 6400lbs)
