DECREASE TOO MUCH WHEN THE PNEUMATIC LOAD WAS APPLIED TO THE APU?
NO ENGINE SPEED DECREASES TOO MUCH WHEN A BLEED LOAD IS APPLIED (FIG. 121).
Bleed Air for Main Engine Start Is Not Sufficient
Figure 123A (Sheet 2)
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BLEED AIR VALVE PREREQUISITES
OPERATES OPEN AND MAKE SURE THIS SYSTEM WILL OPERATE:
CLOSED AGAIN AND APU (AMM 49-11-00/201)
AGAIN
POSSIBLE CAUSES:
1.
BLEED AIR VALVE, V56, PROBLEM (AMM 49-52-11/401)
2.
CLOGGED FILTER FOR THE DIFFERENTIAL PRESSURE REGULATOR (AMM 49-52-21/301)
3.
DIFFERENTIAL PRESSURE REGULATOR PROBLEM (AMM 49-52-21/401)
4.
APU CONTROL THERMOSTAT PROBLEM (AMM 49-52-32/401).
FAULT ISOLATION:
Bleed Air Valve Operates Open and Closed Again and Again
Figure 124
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITHOUT THE ETC ú
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PREREQUISITES
MAKE SURE THIS SYSTEM WILL OPERATE: APU (AMM 49-11-00/201)
BLEED AIR VALVE OPERATES OPEN AND CLOSED AGAIN AND AGAIN
Bleed Air Valve Operates Open and Closed Again and Again
Figure 124A
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PREREQUISITES
MAKE SURE THE AIRPLANE IS IN THIS CONFIGURATION: ELECTRICAL POWER IS ON (AMM 24-22-00/201)
APU ENGINE SPEED DECREASES
POSSIBLE CAUSES:
1.
INLET DOOR SWITCH, S284, PROBLEM OR ADJUSTMENT (AMM 49-15-00/501)
2.
INTERMITTENT ELECTRICAL SIGNAL TO THESE COMPONENTS: . FUEL SOLENOID VALVE (AMM 49-31-31/401) . SEQUENCING SWITCH FOR THE OIL PRESSURE (AMM 49-61-41/401) . ELECTRONIC SPEED SWITCH, S634, (AMM 49-61-22/401).
3.
APU CONTROL UNIT, M280, PROBLEM (AMM 49-61-11/401).
FAULT ISOLATION:
NO
1 DO A CHECK OF THE ADJUST-
MENT OF THE INLET DOOR SWITCH,
S284 (AMM 49-15-00/501).
IS THE INLET DOOR SWITCH ADJUSTED CORRECTLY?
YES YES
2 REMOVE THE INLET DOOR
52 REPAIR THE DAMAGE THAT YOU
SWITCH, S284, CONNECTOR D1246. FIND.
IS THERE DAMAGE TO THE IF NECESSARY, REPLACE THE
CONNECTOR? INLET DOOR SWITCH, S284.
NO
NO
YES NO4 EXAMINE THE CIRCUIT FROM
THE INLET DOOR SWITCH, S284,
CONNECTOR D1246, PIN 4, TO THE
APU CONTROL UNIT, M280, CON-
NECTOR D50B, PIN 46
(WDM 49-31-01).
IS THE CIRCUIT OK?
YES SEE SHEET 2
(BLOCK 21)
APU Engine Speed Decreases
Figure 125 (Sheet 1)
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PART NUMBER 305593 ú
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FROM SHEET 1 (BLOCK 4) YES
NO
21 MEASURE THE RESISTANCE AT THE ELECTRONIC SPEED SWITCH, S634, CONNECTOR D1245, FROM PINS C TO D, J TO M, K TO L (WDM 49-31-01). 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：737-300 400 500 AMM 飞机维护手册 AIRBORNE AUXILIARY POWER 1(46)
