14.  
THE DUCT PRESSURE FROM THE PNEUMATIC SYSTEM IS TOO LOW (AMM 36-11-00/101, FIG. 104)

15.  
THE AIRFLOW FROM THE AIR CONDITIONING PACKS IS NOT SUFFICIENT TO MAINTAIN CABIN PRESSURE (AMM 21-51-00/501).

The Cabin Pressure Control System (CPCS) Cannot Maintain Cabin Pressure Due to
Excessive Air Leakage or There Is a Problem with the Air Supply System
Figure 105 (Sheet 1)

F61008
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
FAULT ISOLATION:

YES
SEE SHEET 3 (BLOCK 3)

50 EXAMINE THE DOOR SEALS FOR DAMAGE AND REPAIR OR REPLACE THE DOOR SEALS IF THERE IS DAMAGE (AMM 52-09-10/ 801).
NOTE:MAKE SURE YOU LOOK AT THE LOWER CORNERS OF THE CARGO DOOR SEALS.

51 DO THE APPLICABLE STEPS
WHICH CORRESPOND TO THE TEST
PINS (OR TEST JACKS) WHICH
HAD THE VOLTAGE PROBLEM:

1.
REPLACE THE CABIN PRESSURE CONTROL MODULE (AMM 21-31-25/401) IF THERE WAS A PROBLEM WITH THE VOLTAGES MEASURED AT TEST PINS A,B,C,E OR G (OR TEST JACKS 1,2,3,5 OR 7)

2.
REPLACE THE AFT OUTFLOW VALVE (AMM 21-31-11/401) IF THERE WAS A PROBLEM WITH THE VOLTAGES MEASURED AT TEST PINS J,K, OR L (OR TEST JACKS 9,10, OR 11). IF THE PROBLEM CONTINUES, REPLACE THE CABIN PRESSURE

SEE SHEET 3 CONTROLLER (AMM 21-31-21/ (BLOCK 31) 401)
3.
REPLACE THE CABIN PRESSURE CONTROLLER (AMM 21-31-21/ 401) IF THERE WAS A PROBLEM WITH THE VOLTAGES MEASURED AT TEST PINS M,N,P, OR R (OR TEST JACKS 12,13,14, OR 15)

4.
REPLACE THE CAPTAIN'S ALTIMETER (AMM 34-12-21/ 401) IF THERE WAS A PROBLEM WITH THE VOLTAGES MEASURED AT TEST PIN D (OR TEST JACK 4). IF THE PROBLEM CONTINUES, DO A CHECK OF THE WIRING BETWEEN THE CAPTAIN'S ALTIMETER AND THE CABIN PRESSURE CONTROLLER (WDM 21-34-01)

5.
REPLACE THE FIRST OFFICER'S ALTIMETER (AMM 34-12-21/ 401) IF THERE WAS A PROBLEM WITH THE VOLTAGES MEASURED AT TEST PIN F (OR TEST JACK 6). IF THE PROBLEM CONTINUES, DO A CHECK OF THE WIRING BETWEEN THE FIRST OFFICER'S ALTIMETER AND THE CABIN PRESSURE CONTROLLER (WDM 21-34-01).

The Cabin Pressure Control System (CPCS) Cannot Maintain Cabin Pressure Due to
Excessive Air Leakage or There Is a Problem with the Air Supply System
Figure 105 (Sheet 2)

F61031
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
FROM SHEET 2 FROM SHEET 2 (BLOCK 2) (BLOCK 30)

YES

NO
NO

31 DO THIS TASK:
52 REPLACE THE OUTFLOW VALVE
"OUTFLOW VALVE HEATED GASKET HEATED GASKET (AMM 21-31-12/
ADJUSTMENT/TEST"201).
(AMM 21-31-12/201).

IF THE PROBLEM CONTINUES,
DID THE OUTFLOW VALVE DO A CHECK OF THE WIRING AND HEATED GASKET OPERATE REPAIR THE PROBLEMS THAT YOU NORMALLY? FIND.

YES
NO

32 DO THIS TASK: 53 REPLACE THE FORWARD OUT-"FORWARD OUTFLOW VALVE SYSTEM FLOW VALVE (AMM 21-43-11/401). TEST" (AMM 21-43-11/501). IF THE PROBLEM CONTINUES,
DID THE FORWARD OUTFLOW DO A CHECK OF THE WIRING AND VALVE OPERATE NORMALLY? REPAIR THE PROBLEMS THAT YOU FIND.
YES

54 DO THE "FLOW AND PRIMARY
HEAT EXCHANGER TEST" FOR EACH
AIR CONDITIONING PACK IN THIS
TASK: "OPERATIONAL TEST - AIR
CYCLE SYSTEM" (AMM 21-51-00/
501).
 REPLACE THE COMPONENT(S) OF EACH AIR CONDITIONING PACK WHICH CAUSED THE LOW AIR FLOW PROBLEM.
 IF THE PROBLEM CONTINUES, DO A CHECK OF THE WIRING AND REPAIR THE PROBLEMS THAT YOU FIND.

DO THIS TROUBLESHOOTING
"LOW DUCT PRESSURE.
THE ENGINE WAS THE BLEED
SOURCE" (AMM 36-11-05/101,
REPAIR THE PROBLEMS THAT

EXAMINE THE AIRPLANE FOR LEAKAGE (AMM 05-51-91/201). REPAIR ALL THE AREAS OF LEAKAGE THAT YOU FIND. LEAKAGE?

YES SEE SHEET 4
(BLOCK 5)

The Cabin Pressure Control System (CPCS) Cannot Maintain Cabin Pressure Due to
Excessive Air Leakage or There Is a Problem with the Air Supply System
　
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