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A
747-400 MAINTENANCE MANUAL
 BLEED AIR OVERPRESSURE SWITCH - ADJUSTMENT/TEST
_______________________________________________
 1.  General
_______
 A.  This procedure contains one task. It does a functional test of the bleed air overpressure indication system. The overpressure switch itself, however, is not tested in-situ. Therefore, in order to complete this functional test in a timely and practical manner, it is necessary to replace the switch that is removed, with a new switch or a shop tested switch that is known to be in serviceable condition.
 NOTE: The switch that is removed by this test procedure can also be
____ sent to the shop to be tested per the component maintenance manual for serviceability and reinstalled on the airplane again.
 B.  To get access to the overpressure switch it is necessary to extend the leading edge flaps.
 TASK 36-21-03-705-045
 2.  Overpressure Switch Functional Test
___________________________________
 A.  References
 (1)  
AMM 24-22-00/201, Manual Control

 (2)  
AMM 27-81-00/201, Leading Edge Flap System

 (3)  
AMM 31-61-00/201, Integrated Display System

 (4)  
AMM 36-21-03/401, Bleed Air Overpressure Switch

 (5)  
AMM 45-10-00/201, Central Maintenance Computer System

 B.  
Access

 (1)  
Location Zone
 452 System 1 - Right Upper Half Strut
 462 System 2 - Right Upper Half Strut
 472 System 3 - Left Upper Half Strut
 482 System 4 - Left Upper Half Strut

 C.  
Prepare to Do the Functional Test

 (1)  
Supply electrical power (AMM 24-22-00/201).

 S 865-006

 (2)  
Make sure these circuit breakers are closed:

 (a)  
On the overhead circuit breaker panel, P7: 1) 7F09, EIU L 2) 7F10, EIU C 3) 7F15, EIU R

 (3)  
Make sure there is no pressure in the pneumatic system.

 S 865-002
 S 215-077
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747-400 MAINTENANCE MANUAL
 S 865-050
 (4) Do this task: Leading Edge Flap Extension (AMM 27-81-00/201).
 S 015-007
 WARNING: YOU MUST CAREFULLY DO THE STEPS IN THE TASK BELOW TO INSTALL
_______ THE LE FLAP SAFETY LOCKS. THE LE FLAPS CAN MOVE QUICKLY IF YOU DO NOT INSTALL THE SAFETY LOCKS CORRECTLY. THIS CAN CAUSE INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT.
 (5)  
Do this task: Extended Leading Edge Flap Deactivation and Safety Lock Installation (AMM 27-81-00/201).

 S 715-047

 (6)  
Do the steps that follow to make sure the bleed air overpressure switch wiring has continuity.

 (a)  
Get access to the CMCS input monitoring (AMM 45-10-00/201).

 (b)  
Use the CDU keyboard to enter the applicable input code as follows: ~............................................................ | E/59/352/10 (Engine 1) | E/59/352/01 (Engine 2) | .............................................................. | E/59/352/11 (Engine 3) | E/59/352/00 (Engine 4) | 2..............................….............................1

 (c)  
Make sure that bit 12 is set to 1.

 NOTE: When bit 12 is set to 1, there is no overpressure
____
 condition.

 (d)  Do not exit CMCS input monitoring.
 S 715-048
 (7)  Make sure that the SYS FAULT lights for all four engines on the bleed overhead panel does not come on.
 D. Do the Functional Test
 S 035-059
 WARNING: THE BLEED AIR OVERPRESSURE SWITCH CONNECTORS WILL HAVE
_______ ELECTRICAL POWER APPLIED DURING THE TEST. TAKE STEPS TO AVOID ELECTRICAL SHOCK.
 (1)  
Disconnect the electrical connector from the applicable overpressure switch that follows:
　
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