INCREASE Ps TO 60-70 PSIG. IS Pc ABOVE 20 PSIG?
 IS Pc ABOVE 20 PSIG?

NO YES
SEE SHEET 4 SEE SHEET 4 (BLOCK 23) (BLOCK 9)

Low Duct Pressure. The Engine Was the Bleed Source.
Figure 104 (Sheet 3)

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C45344
A

737-300/400/500
MAINTENANCE MANUAL

FROM SHEET 3 FROM SHEET 3 (BLOCK 8) (BLOCK 22)

YES
NO
YES
23 DECREASE Ps TO ZERO. RECONNECT THE 450`F SENSE LINE.
 DISCONNECT THE CONTROL PRESSURE SENSE LINE TO THEPRSOV AT THE TEE AND INSTALL A CAP ON THE SENSE LINE (SEE SHEET 10, VIEW G).
INCREASE Ps TO 60-70 PSIG. IS Pc ABOVE 20 PSIG?
NO
NO

9 DECREASE Ps TO ZERO, AND
REMOVE ALL THE PRESSURE GAUGES
AND ASSOCIATED HARDWARES
INSTALLED IN THE PREVIOUS
STEPS AND RECONNECT THE TUBES.

CHECK THE POSITION INDICA-TOR ON THE HIGH-STAGE VALVE
(SEE SHEET 11).

IS THE VALVE IN THE FULLY
CLOSED POSITION?

YESNO

10 USE A WRENCH TO OPEN AND
CLOSE THE HIGH-STAGE VALVE.
DID IT OPEN AND CLOSE
SMOOTHLY?

YES YES

11 CONNECT A SUPPLY PRESSURE
GAUGE (Ps), PRESSURE REGULA-TOR, AND A NITROGEN BOTTLE TO
THE SUPPLY PORT ON THE HIGH-STAGE REGULATOR (SEE
SHEET 12).

SLOWLY INCREASE Ps TO
70 PSIG.

 EXAMINE THE CONTROL PRES-SURE SENSE LINES FROM THE
HIGH-STAGE REGULATOR TO THE
HIGH-STAGE VALVE FOR LEAKAGE.

 IS THERE ANY LEAKAGE?

NO SEE SHEET 5
(BLOCK 12)

54 DECREASE Ps TO ZERO AND
RELEASE THE AIR PRESSURE IN
THE SYSTEM.
REPAIR THE LEAKAGE.
Low Duct Pressure. The Engine Was the Bleed Source.
Figure 104 (Sheet 4)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
C45349
A 737-300/400/500MAINTENANCE MANUAL
FROM SHEET 4 (BLOCK 11)

NO
NO

12 NOTE:____ THIS STEP CHECKS
THE HIGH-STAGE
VALVE FOR INTERNAL
LEAKAGE. A LEAKY
ACTUATOR CAN CAUSE
LOW DUCT PRESSURE.

DISCONNECT THE CONTROL PRESSURE LINE AT THE HIGH-STAGE VALVE.
USE A WRENCH TO MANUALLYPUT THE HIGH-STAGE VALVE INTHE OPEN POSITION. WHILE YOU HOLD THE HIGH-STAGE VALVE IN THE OPEN POSITION, PUT YOUR THUMB OVER THE HIGH-STAGE VALVE PORT (SEE SHEET 13), THEN REMOVE THE WRENCH AND LET THE HIGH-STAGE VALVE MOVE TO THE CLOSED POSITION.
MONITOR THE AMOUNT OF TIME IT TAKES FOR THE HIGH-STAGEVALVE TO GO TO THE FULLY CLOSED POSITION.
DID IT TAKE MORE THAN 10 SECONDS?
YES
NO

13 NOTE: RECONNECT THE SUP-PLY PRESSURE LINE
AT THE HIGH-STAGE
VALVE. THIS STEP
CHECKS THE CONTROL
PRESSURE OF THE
HIGH-STAGE REGULA-TOR. IF THE CON-TROL PRESSURE IS
LOW, THE DUCT PRES-SURE WILL BE LOW.

DISCONNECT THE CONTROL PRESSURE SENSE LINE AT THEHIGH-STAGE REGULATOR.
INSTALL A CONTROL PRES-SURE GAUGE (Pc) TO THE CONTROLPRESSURE LINE (SEE SHEET 14).
SLOWLY INCREASE Ps TO 35-40 PSIG. IS Pc ABOVE 14.0 PSIG?
YES

57 REDUCE Ps TO ZERO.
 REPLACE THE 450`F THERMO-STAT (AMM 36-12-55/401), AND THE PRECOOLER CONTROL VALVE SENSOR (AMM 36-12-45/401).
56 REDUCE Ps TO ZERO. REPLACE THE HIGH-STAGEREGULATOR (AMM 36-11-86/401).

Low Duct Pressure. The Engine Was the Bleed Source.
Figure 104 (Sheet 5)

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B06041
A 737-300/400/500MAINTENANCE MANUAL
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