S 035-034

 (2)  
Disconnect the electrical connector from the overtemperature switch.

 (3)  
Install the overtemperature switch (Ref 21-61-07/401).

 S 425-025
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 ALL  ú ú 01 Page 505 ú Jun 10/94
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A
747-400 MAINTENANCE MANUAL
 TRIM AIR PRESSURE REGULATING AND SHUTOFF VALVE - REMOVAL/INSTALLATION
 1.  General_______
 A.  This procedure has two tasks. The first task is the removal of the trim air pressure regulating and shutoff valve (trim air PRSOV). The second task is the installation of the trim air PRSOV.
 B.  The trim air PRSOV is on the left side of the keel beam and aft of the No. 2 air conditioning pack.
 TASK 21-61-08-004-001
 2.  Trim Air Pressure Regulating and Shutoff Valve Removal (Fig. 401)______________________________________________________
 A.  References
 (1)
AMM 06-09-03/201, Body Section 44 Access Doors and Panels

 (2)
AMM 24-22-00/201, Manual Control

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

 (4)
AMM 36-00-00/201, Pneumatic Sytem

 (5)
AIPC 21-61-68, Fig. 4

 (6)
AIPC 21-61-10, Fig. 10

 (7)
AIPC 21-61-10, Fig. 10A

 (8)
AIPC 21-21-56, Fig. 2

 (9)
WDM 21-61-93

 (10)
 SSM 21-61-05

 B.  Access
 (1)  
Location Zone
 133 Air Conditioning Equipment Bay, LH

 (2)  
Access Panels
 191M-L Air Conditioning Access Panel

 C.  Prepare to Remove the Trim Air PRSOV
 S 864-002
 (1)
Supply electrical power (AMM 24-22-00/201).

 (2)
Supply power to EICAS (AMM 31-61-00/201).

 (3)
Remove the pressure in the pneumatic system (AMM 36-00-00/201).

 S 864-038
 S 864-006
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 21-61-08
 ALL  ú ú 02 Page 401 ú Jun 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

747-400
MAINTENANCE MANUAL

BONDING
ELECTRICAL
JUMPER
CONNECTOR
FWD
TRIM AIR PRESSURE REGULATING AND SHUTOFF VALVE
A
CABIN SENSE LINE
CLAMP (2 PLACES)
SEE B FWD
DOWNSTREAM SENSE LINE
TEE FITTINGS (2 PLACES -NOT SHOWN) TRIM AIR PRESSURE REGULATING AND SHUTOFF VALVE
SEE A
CLAMP
DUCT
SEAL
VALVE ASSEMBLY
B
Trim Air Pressure Regulating and Shutoff Valve Installation
Figure 401

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 ALL  ú ú 01 Page 402 ú Oct 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 S 864-039
 (4)  Release the air which is in the trim air ducts:
 (a)  
Turn the FLT DECK selector to the MAN position on the P5 overhead panel.

 (b)  
Turn and hold the FLT DECK selector to the W position while you monitor the EICAS ECS maintenance page.

 (c)  
Make sure the TRIM VAL POS F/D indication, on the EICAS ECS maintenance page, is between 0.90 and 1.00.

 NOTE: The trim air PRSOV will open and permit the air in the
____ trim air ducts to be released.
 (d)  
Turn the FLT DECK temperature selector to the AUTO position.

 (e)  
Make sure the TRIM AIR PRESS indication, on the EICAS ECS maintenance page, is approximately 0.

 (f)  
Make sure the two DUCT PSI indications (left and right), on the EICAS ECS synoptic page, are approximately 0.
　
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