BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
F11692
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 2 YESYES
(BLOCK 4)
25 REMOVE THE COOLING FAN
(AMM 49-51-11/401).
 DO THESE STEPS:
. DO A CHECK OF THE APU
GENERATOR FOR DAMAGE
. DO A CHECK OF THE OIL COOLER
FOR BLOCKAGE AND DAMAGE

. DO A CHECK OF THE OIL FILTER ELEMENT FOR BLOCKAGE AND METAL PARTICLES (AMM 49-91-12/401)
. DO A CHECK OF THE APU FOR INTERNAL DAMAGE (AMM 49-21-00/601).
DO YOU FIND THE PROBLEMS ABOVE?

65 DO THESE STEPS:
. IF THE APU GENERATOR IS DAMAGED, REPLACE THE APU GENERATOR (AMM 24-21-21/ 401)
. IF THE OIL COOLER IS BLOCKED, REMOVE THE BLOCKAGE
. IF THERE IS DAMAGE TO THE OIL COOLER, REPLACE THE OIL COOLER (AMM 49-91-41/401)
. IF THE OIL FILTER IS BLOCKED AND HAS METAL PART-ICLES, REPLACE THE APU (AMM 49-11-00/401)
. IF THE OIL FILTER IS BLOCKED AND HAS NO METAL PARTICLES,

Automatic Shutdown - HIGH OIL TEMP or FAULT Light Is On
Figure 137 (Sheet 5)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
H24603
PREREQUISITES
MAKE SURE THIS SYSTEM WILL OPERATE:

AUTOMATIC SHUTDOWN -
APU (AMM 49-11-00/201)
"OVERSPEED" LIGHT
MAKE SURE THE AIRPLANE IS IN THIS CONFIGURATION:
IS ON

ELECTRICAL POWER IS ON (AMM 24-22-00/201)
POSSIBLE CAUSES:
1.
APU CONTROL UNIT, M280, PROBLEM (AMM 49-61-11/401)

2.
ELECTRONIC SPEED SWITCH, S634, PROBLEM (AMM 49-61-22/401)

3.
TACHOMETER GENERATOR PROBLEM (AMM 49-61-61/401)

4.
FUEL CONTROL UNIT PROBLEM (AMM 49-31-11/401)

5.
APU INTERNAL DAMAGE (AMM 49-11-00/401).

FAULT ISOLATION:
NO NO

1 MAKE SURE THE APU MASTER
21 PRESS THE "OVERSPEED
SWITCH IS IN THE "OFF" RESET" BUTTON ON THE APU
POSITION. CONTROL UNIT.

DOES THE APU CONTROL UNIT DID THE "OVERSPEED" LIGHTHAVE THE "TEST PASS" AND "TEST GO OFF? FAIL" LIGHTS?

YES
YES

NO

2 PRESS THE "OVERSPEED
RESET/TEST" BUTTON ON THE APU
CONTROL UNIT.

DID THE "TEST PASS" LIGHT (GREEN) COME ON?

YES YES

3 START THE APU
54 DO THE APU USUAL SHUTDOWN (AMM 49-11-00/201). (AMM 49-11-00/201). DID THE APU START AND
THE SYSTEM IS OK. OPERATE CORRECTLY?
NO NO

55 DO THE TROUBLESHOOTING FOR APU START PROBLEMS.
YES SEE SHEET 2
(BLOCK 5)

Automatic Shutdown - OVERSPEED Light Is On
Figure 138 (Sheet 1)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 1 (BLOCK 4)

NO

NO
5
EXAMINE THE CIRCUIT FROM
THE ELECTRONIC SPEED SWITCH,
S634, CONNECTOR D1245, PIN E,
TO THE APU CONTROL UNIT, M280,
CONNECTOR D50B, PIN 35
(WDM 49-31-01).

 IS THE CIRCUIT OK?

SPEED SWITCH, S634 (AMM 49-11-00/201). (AMM 49-61-22/401). THE SYSTEM IS OK. START THE APU (AMM 49-11-00/201). DID THE APU START AND OPERATE CORRECTLY?
NO YES NO

7 DID THE "OVERSPEED" SHUT-22 MOVE THE APU MASTER SWITCH
DOWN OCCUR IN LESS THAN TO THE "OFF" POSITION.
30 SECONDS FROM THE TIME THE EXAMINE THE CIRCUITS FROM
APU IS STARTED? THE ELECTRONIC SPEED SWITCH,

S634, CONNECTOR D1245,
NO
PINS G,H, TO THE TACHOMETER GENERATOR, CONNECTOR D1262, PINS C,A (WDM 49-31-01; 49-41-01).
ARE THE CIRCUITS OK?
YES

YES

23 REPLACE THE FUEL CONTROL
UNIT (AMM 49-31-11/401).
 START THE APU
(AMM 49-11-00/201).
 DID THE APU START AND
　
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