(4)  
WDM 28-41-13

 B.
Access

 (1)  
Location Zone 521 Leading Edge to Front Control Spar, Left

 (2)  
Access Panel
 521CB Refuel Control Panel Access Door

 C.
Procedure

 S 434-006
 (1)  
Connect the electrical connector to the fuel quantity indicator.

 S 424-011

 (2)  
Put the fuel quantity indicator in the correct position on the P42 panel.

 S 434-012

 (3)  
Hold the fuel quantity indicator in its position and tighten the screw above the indicator.

 S 864-019

 (4)  
Supply electrical power (AMM 24-22-00/201).

 S 864-013

 (5)
Remove the DO-NOT-CLOSE tags and close these circuit breakers:

 (a)  
On the main power distribution center, P6: 1) 6D5, FUEL QTY 1 2) 6D6, FUEL QTY 2

 (b)  
On the power distribution panel, P180: 1) 180M9, FUELING PWR - HOT BAT

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747-400 MAINTENANCE MANUAL
 (c)  2) 180C25, FUELING LTS PANEL 3) 180C26, FUELING LTS RECPOn the left power distribution center, P414: 1) 414F22, FUELING PWR
 (6)  S 214-007Look at the fuel quantity indicators and make sure there is a fuel quantity indication.
 (7)  S 864-018Push the TEST GUAGES switch on the P42 panel.
 (8)  S 214-014Make sure all the displays on the fuel quantity indicator show 888.8.
 (9)  S 864-016Release the TEST GAUGES switch.
 S 214-017

 (10)
 Make sure the displays go to the usual indication.

 S 414-008

 (11)
 Close the access door of the refuel control panel (521CB).

 S 864-020

 (12)
 Remove the electrical power, if it is not necessary (AMM 24-22-00/201).

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
 FUEL QUANTITY INDICATING SYSTEM - WIRE BUNDLE - REMOVAL/INSTALLATION
____________________________________________________________________
 1.  General (Fig. 401)_______
 A.  This procedure contains four tasks that remove and install wire bundles used for the Fuel Quantity Indicating Systems (FQIS).
 B.  The quantity and location of these wire bundles are as follows:
 (1)  
Six in the left wing tanks that start at the connectors installed on the spar.

 (2)  
Six in the right wing tanks that start at the connectors installed on the spar.

 (3)  
Three in the center wing tank from the connectors installed on the bulkhead.

 C.  
The FQIS wire bundles supply the electrical connection between the tank sensors and the fuel quantity processor unit. This procedure only contains the wire bundle segments in the fuel tanks.

 (1)  
Fuel tank electrical wire bundles that start from the spar/bulkhead connectors in each tank are:

 (a)  
One wire bundle for the densitometer (except the reserve tanks).

 (b)  
One wire bundle for the single point sensors (inboard main and center tank only).

 (c)  
One wire bundle for the fuel quantity tank units and compensators.

 (2)  
The wire bundle for the fuel quantity tank units and compensators contain:

 (a)  
One LO-Z (low impedance) wire for each tank unit and the compensator. The LO-Z wires are not shielded.

 (b)  
One HI-Z (high impedance) shielded wire between the spar connector and the compensator HI-Z terminal. The shield stops at the compensator.

 (c)  
The HI-Z wire routing is parallel to the LO-Z wires but is in a bundle that is isolated.

 (3)  
A second HI-Z wire (daisy chain) is installed in each tank. This wire does not start at the spar connector.
　
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