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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

ELECTRICAL  BLEED AIR OVERPRESSURE SWITCH  JAMNUT WASHER 
ENGINE 3  CONNECTOR 
BLEED AIR  WING RIB 
OVERPRESSURE  PRESSURE 
SWITCH  SENSING 
ENGINE 4  SEE  A  TUBE 
BLEED AIR 
OVERPRESSURE  DRAIN HOLES 
SWITCH 
SEE  B 

BLEED AIR PRESSURE SENSOR
FWD
ENGINE 3 BLEED AIR OVERPRESSURE SWITCH (ENGINE 2 BLEED AIR OVERPRESSURE SWITCH IS OPPOSITE)
A
BLEED AIR JAMNUTPRESSURE WASHERSENSOR DRAIN
HOLES
PRESSURE SENSING TUBE
WING RIB
BLEED AIR
ELECTRICAL OVERPRESSURE
CONNECTOR
SWITCH  FWD
ENGINE 4 BLEED AIR OVERPRESSURE SWITCH (ENGINE 1 BLEED AIR OVERPRESSURE SWITCH IS OPPOSITE)
B
Bleed Air Overpressure Switch Installation
Figure 401

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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L98693
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747-400 MAINTENANCE MANUAL
 S 864-004
 WARNING: YOU MUST RELEASE THE PRESSURE IN THE PNEUMATIC DUCT BEFORE YOU
_______ REMOVE A PNEUMATIC SYSTEM COMPONENT. THE HOT, HIGH PRESSURE AIR CAN CAUSE INJURIES TO PERSONS.
 (3)
Release the pressure in the pneumatic system (AMM 36-00-00/201).

 S 864-050

 (4)  
Open the applicable circuit breaker and attach a DO-NOT-CLOSE tag.

 (a)  
P6 Main Power Distribution Panel
 1) 6H32 ENG 1 AIR SUPPLY CONT
 2) 6H33 ENG 2 AIR SUPPLY CONT
 3) 6H34 ENG 3 AIR SUPPLY CONT
 4) 6H35 ENG 4 AIR SUPPLY CONT

 D.
Remove the Bleed Air Overpressure Switch

 S 034-006
 (1)  
For the applicable engine, disconnect the electrical connector from the switch:

 (a)
Engine 1 - DS1590 BLEED AIR OVERPRESSURE SWITCH

 (b)
Engine 2 - DS1591 BLEED AIR OVERPRESSURE SWITCH

 (c)  
Engine 3 - DS1592 BLEED AIR OVERPRESSURE SWITCH

 (d)  
Engine 4 - DS1593 BLEED AIR OVERPRESSURE SWITCH

 S 034-007
 (2)  
Disconnect the pressure sensing tube from the overpressure switch.

 S 034-021

 (3)  
Remove the jamnut and the washer.

 S 024-022

 (4)  
Remove the bleed air overpressure switch.

 S 214-055

 (5)
Inspect the pressure sensing tube drain hole for obstructions.

 S 034-009

 (6)  
Put a cover on the opening for the pressure sensing tube to keep out unwanted objects.

 TASK 36-21-03-404-010
 3. Install the Bleed Air Overpressure Switch (Fig. 401)
_________________________________________
 A. Consumable Materials
 (1)  
G00095 Detector - Leak, Leak-Tek (160X)

 B.
References

 (1)  
AMM 24-22-00/201, Manual Control

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

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747-400
MAINTENANCE MANUAL

 (3)  
AMM 36-00-00/201, Pneumatic System

 (4)  
AMM 45-10-00/201, Central Maintenance Computer System

 (5)  
AMM 71-00-00/201, Power Plant

 (6)  
IPC 36-21-03, Fig. 1

 C. Access
 (1)  
Location Zones
 452 Engine 1 - Right Upper Half Strut
 462 Engine 2 - Right Upper Half Strut
 472 Engine 3 - Left Upper Half Strut
 482 Engine 4 - Left Upper Half Strut

 (2)  
Access Panel
 521AB Left Access Panel, Lower Inboard Nacelle
 521AB Left Access Panel, Lower Skin Leading Edge
　
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