Fuel Gauge and Low Fuel Warning Indicator
WARNING: This page is about a different car, the 2004 Ford RV Cutaway, 2004 Ford Econoline, 2004 Ford E450 Super Duty, and 2004 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
The fuel level sender is hardwired to the instrument cluster. The instrument cluster sends a signal voltage to the fuel level sender, which contains a variable resistor. The instrument cluster uses the return voltage to determine fuel level. When the fuel gauge reads approximately 1/8th tank, the instrument cluster illuminates the low fuel warning indicator.