24-51-01
 ALL  ú ú 01 Page 406 ú Jun 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 MAIN DECK CARGO HANDLING RELAYS - REMOVAL/INSTALLATION
______________________________________________________
 1.  General_______
 A.  The following describes procedures for removing and installing the main deck cargo handling relays R991 and R992.
 B.  The main deck cargo handling relays are mounted inside the P715 auxiliary/external No. 2 power center. The P715 auxiliary/external No. 2 power center is located in the electrical and electronics compartment.
 C.  Access to the electrical and electronics compartment is gained by the small access door behind the nose wheel from outside the airplane or through the forward cargo compartment.
 TASK 24-51-04-004-029
 2.  Remove Main Deck Cargo Handling Relay (Fig. 401)_____________________________________
 A.  References
 (1)  
24-22-00/201, Manual Control

 (2)  
IPC 24-51-60 Fig. 2

 (3)  
WDM 24-51-81

 (4)  
SSM 24-51-09

 B.  
Access

 (1)  
Location Zone 118 Electrical and Electronics Compartment, RH

 (2)  
Access Panel
 P715 Aux/Ext No. 2 Power Center

 C.  
Procedure

 S 864-003
 (1)  
Remove electrical power from airplane, if not already accomplished (Ref 24-22-00/201).

 S 864-004

 (2)  
Verify BATTERY switch, located on the P5 overhead panel, is set to the OFF position and attach DO-NOT-OPERATE identifier.

 (3)
Open P715 panel access door to gain access to applicable relay.

 S 034-006

 (4)  
Remove the upper terminal cover from relay by removing two screws securing cover.

 S 014-005
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 24-51-04
 DECK CARGO HANDLING  ú ú 02 Page 401 ú Jun 10/90
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

747-400
MAINTENANCE MANUAL

MAIN DECK CARGO HANDLING BUS RELAY 2 (R992)
SEE A SEE B
MAIN DECK CARGO HANDLING BUS RELAY 1 (R991)
SEE B
P715 AUX/EXT NO. 2
POWER CENTER

A

MAIN DECK CARGO HANDLING BUS RELAY (TYPICAL)
____  B
NOTE: TERMINAL LEADS NOT SHOWN FOR CLARITY.
Main Deck Cargo Handling Bus Relay Installation Figure 401
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH MAIN ú

 24-51-04
 DECK CARGO HANDLING  ú ú 02 Page 402 ú Jun 10/90
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 S 034-007
 (5)  Remove upper terminal nuts and washers that secure each of the terminal leads to the relay and disconnect leads.
 NOTE: Identify each of the terminal leads that connect to
____ the removed relay for reinstallation.
 S 034-008
 (6)  
Remove lower terminal cover from relay.

 S 034-009

 (7)  
Remove lower terminal nuts and washers that secure each of the terminal leads to the relay and disconnect leads.

 NOTE: Identify each of the terminal leads that connect to
____ the removed relay for reinstallation.
 S 034-010
 (8)  
Reinstall terminal nuts and washers to relay. Tighten finger-tight.

 S 034-011

 (9)  
Reinstall terminal covers on relay.

 S 034-012

 (10)
 Remove four screws securing applicable relay to panel.

 S 024-013

 (11)
 Remove applicable relay from panel.

 TASK 24-51-04-404-028
 3. Install Main Deck Cargo Handling Relay (Fig. 401)
______________________________________
 A. References
 (1)  
24-22-00/201, Manual Control

 (2)  
AMM 45-10-00/201, Central Maintenance Computer System

 (3)  
　
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