Low Fuel Lamp/Indicator: Description and Operation
How the Circuit WorksThe indicator lights are controlled by different conditions in their associated systems. Refer to each associated system to see its entire schematic.
Low Fuel Indicator Light
WARNING: Do not smoke while working on the fuel system. Keep open flame away from the work area. Drain fuel only into an approved container.
A thermistor is mounted in the fuel tank unit. When the thermistor is cool, its resistance is very high. When the thermistor's temperature increases, its resistance decreases. Fuel in the fuel tank transfers heat away from the thermistor fast enough to keep it cool so the thermistor's resistance stays high and the low fuel indicator light does not come on. When the fuel level drops below the thermistor, the thermistor's temperature increases. With less and less fuel to cool it, the thermistor's resistance decreases, eventually allowing current to flow through the low fuel indicator light and the thermistor to ground, which turns on the low fuel indicator light.