TM 1-1520-240-102-4-52-4-6). The switches are used to test the automatic shut-off features in each tank and to stop refueling when thedesired fuel level is attained in each or all tanks. Six of theseven switched are connected to fuel level control valvesin a specific tank. The seventh switch, labeled ALL TEST,is electrically connected to the fuel level control valves inall six tanks. Setting any of the six switches to PRI OFFor SEC OFF raises the corresponding primary or secon-dary float in the fuel level control valve. This action simu-lates a high fuel level and causes the fuel shutoff valvein that tank to close. Setting the ALL TEST switch to PRIOFF or SEC OFF raises the corresponding float in all sixtanks and shuts off the fuel flow into all tanks simulta-neously.2-4-16. REFUEL VALVE POSN Indicating Lights.The two amber PRESS-TO-TEST REFUEL VALVEPOSN (position) lights (fig. 2-4-6) indicates the status ofthe two refueling valves in the pressure refueling system.The valves are normally closed and prevent fuel feed-back into the aft auxiliary tanks when the aft tank pumpsare operating. While pressure refueling the valves areopened and allow fuel flow from the refueling system intothe aft tank.The valves are controlled by the refueling station PWRON switch. When the switch is ON, the valves areopened and the indicating lights will illuminate momen-tarily indicating valve transition from close to open. Con-versely, when the switch is OFF, the valves are closedand the indicating lights will illuminate momentarily indi-cating valve transition from open to close. A continuouslyilluminated light, with the switch at OFF, indicates theassociated valve is opened and the fuel in the tank willnot be available.
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