D. Install the Bleed Air Overpressure Switch
 S 434-011
 (1)  
Remove the cover from the pressure sensing tube.

 S 424-012

 (2)  
Use the jamnut and the washer to attach the overpressure switch to the support bracket.

 S 434-013

 (3)
Connect the pressure sensing tube to the overpressure switch.

 S 434-014

 (4)  
For the applicable engine, connect the electrical connector to the overpressure 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 864-051
 (5)  
Remove the DO-NOT-CLOSE tag and close the applicable circuit breaker.

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

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747-400 MAINTENANCE MANUAL
 3) 6H34 ENG 3 AIR SUPPLY CONT
 4) 6H35 ENG 4 AIR SUPPLY CONT

 E. Do the Test for the Installation of the Bleed Air Overpressure Switch
 S 794-016
 (1)  
Apply the leak detector to the connection between the pressure sensing tube and the overpressure switch.

 S 794-056

 (2)  
Do Method 1 or method 2 to apply pressurized air to the over pressure switch.

 (a)  
METHOD 1; Dry motor the applicable engine (AMM 71-00-00/201).

 (b)  
METHOD 2; Pressurize the pneumatic system upstream of the PRSOV (AMM 36-00-00/201).

 S 794-018
 (3)  
Examine the overpressure switch for leakage.

 S 864-045

 (4)  
Release the pressure in the pneumatic system (AMM 36-00-00/201).

 S 364-057

 (5)  
If there is leakage, make the necessary repairs.

 S 864-046

 (6)  
Cycle these circuit breakers on the P6 main power distribution panel:

 (a)  
H32 ENG 1 AIR SUPPLY CONT

 (b)  
H33 ENG 2 AIR SUPPLY CONT

 (c)  
H34 ENG 3 AIR SUPPLY CONT

 (d)  
H35 ENG 4 AIR SUPPLY CONT

 S 744-047
 (7)
Wait 4 minutes to allow the ASCTU to perform the BITE check.

 S 734-048

 (8)  
Get access to the CMCS: 21 ECS, SUPPLY, EXISTING FAULTS
 (AMM 45-10-00/201).

 S 714-049

 (9)
Make sure that none of these applicable faults are present:

 (a)
CMCS message 36045 - BLEED 1 OVERPRESSURE SWITCH FAIL

 (b)
CMCS message 36046 - BLEED 2 OVERPRESSURE SWITCH FAIL

 (c)
CMCS message 36047 - BLEED 3 OVERPRESSURE SWITCH FAIL

 (d)
CMCS message 36048 - BLEED 4 OVERPRESSURE SWITCH FAIL

 F.
Put the Airplane Back To Its Usual Condition

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747-400 MAINTENANCE MANUAL
 S 414-052
 WARNING:_______ MAKE SURE THERE ARE NO PERSONS OR EQUIPMENT NEAR THE LE AND TE
 FLAPS AND THE FLAP DRIVE MECHANISMS BEFORE YOU MOVE THE FLAP
 CONTROL LEVER.  WHEN YOU MOVE THE CONTROL LEVER WITH THE
 HYDRAULIC POWER REMOVED, THE ELECTRICAL POWER CAN MOVE THE

 FLAPS AND CAN CAUSE INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT.
 (1)  
Remove the locks and retract the leading edge flaps (AMM 27-81-00/201).

 S 864-020

 (2)  
Remove the electrical power if it is not necessary (AMM 24-22-00/201).
　
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