Low Fuel Lamp/Indicator: Description and Operation

Low fuel indicator (part of instrument cluster)

A thermistor is mounted in the fuel tank as part of the fuel gauge sender. When the thermistor is cool, its resistance is very high. When the thermistor is warm, its resistance lowers. Fuel in the fuel tank transfers heat away from the thermistor fast enough to keep it cool. The thermistor resistance stays high and the low fuel warning light does not operate. When the fuel level drops below about 2.6 gallons, the thermistor is no longer immersed in fuel. Without the fuel to cool it, the thermistor resistance becomes low. Current flows through the low fuel warning light and the thermistor to ground. The low fuel warning indicator lights up. For information about the operation of other indicators, refer to the individual circuit schematics.