21-51-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL

 C. Access
 (1)  
Location Zones
 135/136 Environmental control system (ECS) bay
 211/212 Control cabin

 (2)  
Access Doors
 193HL Environmental control system bay (left)
 194ER Environmental control system bay (right)

 D.
Prepare for the Test

 S 865-403
 (1)  
Supply electrical power (AMM 24-22-00/201).

 S 865-405

 (2)  
Make sure all circuit breakers for the air conditioning system are closed.

 S 865-407

 (3)  
Set these switches and selectors on the air conditioning control panel, P5:

 (a)  
Make sure the TRIM AIR switch is OFF. 1) Make sure the INOP lights for all three zones are on.

 (b)  
Make sure the L (R) pack selectors are OFF. 1) Make sure the L (R) PACK OFF lights are on.

 S 865-189
 (4)  
Make sure the pneumatic power is off (AMM 36-00-00/201).

 (a)  
Make sure the L (R) DUCT PRESS gage on the P5 panel shows less than 5.0 psi.

 S 865-190
 (5)  
Make sure the BLEED AIR L ENG and BLEED AIR R ENG switches on the P5 panel are OFF.

 S 745-191

 (6)  
Do the BITE tests for these components:

 (a)  
Pack temperature controller (AMM 21-51-00/501)

 (b)  
Standby temperature controller (AMM 21-51-00/501).

 (c)  
Zone temperature controller (AMM 21-61-00/501).

 (d)  
APU ECU (AMM 49-11-00/501).

 S 015-265
 (7)  
Make sure the EICAS computer select knob on the EICAS display select panel, P9, is in the AUTO position.

 (8)  
Push the AUTO switch on the display select panel, P7.

 S 215-193

 (9)  
Push the ECS/MSG switch on the EICAS maintenance panel, P61.

 (a)  
Look at the L PACK OUT and the R PACK OUT temperatures on the ECS maintenance page.

 S 865-192
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MAINTENANCE MANUAL

 (b) The difference between the L PACK OUT and the R PACK OUT temperatures must be less than 2 deg. C (5 deg. F).
 S 975-194
 (10)
 Make a measurement of the temperature in all three zones near the zone temperature sensors.

 S 975-195

 (11)
 Compare the temperatures you measured in each zone to the temperatures displayed on the temperature control panel, P5.

 (a)  
The difference between the measured temperatures and the temperatures displayed on the P5 panel must be less than +/- 6 deg. C (+/- 11 deg. F).

 NOTE: This steps makes sure the zone temperature sensors
____
 are accurate.

 S 975-196
 (12) Make a record of the ambient temperature.
 NOTE: You can get the ambient temperature from the control
____ tower, automated transcribed information service (ATIS) or from an independent measurement.
 S 975-197
 (13)
 Compare the ambient temperature to the DUCT TEMP (FLT DK, FWD, and AFT) display on the ECS maintenance page.

 (a)  
The difference between the ambient temperature and the DUCT TEMP display for each zone must be within +/- 6 deg. C (+/- 11 deg. F).

 NOTE: This step makes sure the duct temperature sensors
____
 are accurate.

 The difference between the ambient temperature and the duct temperature can be more than 6 deg. C (11 deg. F) if the air conditioning system was operated in the last 3 hours.
 S 215-198
 (14)
 Make sure the ECS maintenance page has these indications:

 (a)  
L (R) TEMP VALVE is less than 0.07.

 NOTE: This indicates that the left (right) temperature
____ control valves are closed (less than 7% open).
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