Fuel Gauge: Description and Operation

BI-METAL FUEL INDICATOR

This fuel level indicating system consists of a sending unit attached to the fuel reservoir and a fuel gauge mounted on the instrument panel. The bi-metal fuel indicator gauge pointer is attached to a wire-wound bimetal strip which, when heated by the flow of electrical current controlled by the sender unit, produces the appropriate indication. The bi-metal fuel indicator is used with a Instrument Voltage Regulator (IVR), which controls and maintains an average pulsating voltage of 5 volts at the indicator. The fuel sender consists of a variable resistor, controlled by the action of an attached float in the fuel tank. The variable resistor consists of a screened resistive material on a ceramic substrate, which produces a resistance value. On models except Aerostar, Bronco II, Explorer and Ranger, resistance should be 10 ohms (full tank) and 70 ohms (empty tank). On Aerostar, Bronco II, Explorer and Ranger, resistance should be 145 ohms (full tank) and 22.5 ohms (empty tank).

MAGNETIC FUEL INDICATOR

This fuel level indicating system consists of a sending unit attached to the fuel reservoir and a fuel gauge mounted on the instrument panel. The magnetic fuel indicator gauge creates a polarity in the wire windings which, depending on the resistance at the sender, controls the degree of pointer rotation. This gauge operates on battery voltage. The fuel sender consists of a variable resistor, controlled by the action of an attached float in the fuel tank.