Low fuel level warning lights (L FUEL LOW and R FUEL
LOW) for the left and right main tanks are on the master
caution panel. They are activated by 28 volts from the
No. 1 dc bus through a thermistor on the center probe
of each main tank. When the fuel level in a tank drops
to about 370 pounds, the thermistor is uncovered. This
energizes a relay within dual control unit (057A3) to
close and the caution light for that tank comes on.