YES NO NO

8 MOVE THE APU MASTER SWITCH
31 EXAMINE THE CIRCUIT FROM
TO THE "START" POSITION. THE START RELAY R5, TERMINAL
X1, TO THE APU CONTROL UNIT,

NOTE: AFTER THE AIR INLET
M280, CONNECTOR D50B, PIN 30
DOOR CLOSES, 28V DC (WDM 49-31-01).
ENERGIZE THE START
IS THE CIRCUIT OK?
RELAY R5, TO CLOSE FOR
90 SECONDS.

YES MAKE SURE THERE IS 28V DC AT THE START RELAY R5, SEE SHEET 5 TERMINAL X1 AND TERMINAL A2(BLOCK 32) (WDM 49-31-01). IS THERE 28V DC AT TERMINAL X1?

YES SEE SHEET 6
(BLOCK 9)

Starter Motor Does Not Turn
Figure 110A (Sheet 4)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 3876259  ú
 ú  02  Page 147
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
L38608
////////////////////////
A / GTCP85-129 SERIES /
737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 4 (BLOCK 31)

YES
YES
32 DO A CONTINUITY CHECK AT
THE APU CONTROL UNIT, M280,
CONNECTOR D50B, PINS 30 AND 36

(WDM 49-31-01).
IS THERE AN OPEN CIRCUIT?

IS THERE AN OPEN CIRCUIT?

YES
NO

35 EXAMINE THE CIRCUIT FROM
THE APU CONTROL UNIT, M280,
CONNECTOR D50B, PIN 10, TO THE

APU MASTER SWITCH, S248,
CONNECTOR D4218J, PIN 5
(WDM 49-31-01).
IS THE CIRCUIT OK?

REPLACE THE APU CONTROL UNIT, M280 (AMM 49-61-11/401).
IF THE PROBLEM CONTINUES, REPLACE THE APU MASTER SWITCH,S248 (WDM 49-31-01).
Starter Motor Does Not Turn
Figure 110A (Sheet 5)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 3876259  ú ú 02 Page 148 ú Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
L38610
FROM SHEET 4 (BLOCK 8)

Starter Motor Does Not Turn
Figure 110A (Sheet 6)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 3876259  ú ú 02 Page 149 ú Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
L38611
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
PREREQUISITES
MAKE SURE THESE CIRCUIT BREAKERS ARE CLOSED: P6-5 - C33
 J9 BATTERY SHIELD - "AUX POWER UNIT START"
STARTER MOTOR
APU CONTROL UNIT
TURNS SLOWLY

POSSIBLE CAUSES:
1.
STARTER MOTOR, M161, PROBLEM (AMM 49-41-11/401)

2.
APU BATTERY PROBLEM (AMM 24-31-11/201)

3.
APU INTERNAL DAMAGE (AMM 49-11-00/401).

FAULT ISOLATION:
NO

21 _______
WARNING DO NOT OPERATE THE APU WITH YES
THE LOWER SHROUD REMOVED IF PERSONS ARE IN OR DIRECTLY
SEE SHEET 2 (BLOCK 2)
BELOW THE APU COMPARTMENT. YOU MUST BE A MINIMUM OF 3 FEET AWAY FROM THE OUTER EDGE OF THE APU COMPARTMENT OPENING TO OPERATE THE APU WITH THE LOWER SHROUD REMOVED. AN APU TURBINE WHEEL SEPARA-TION DURING OPERATION CAN CAUSE INJURY TO PERSONS.
REPLACE THE APU BATTERY (AMM 24-31-11/201).
 DOES THE PROBLEM CONTINUE?

YES

22 MANUALLY TURN THE APU (AMM 49-21-00/201).
ARE THERE UNUSUAL NOISES WHEN THE APU TURNS OR DOES THEAPU NOT TURN AS USUAL?
NO NO

YES

F11380
Starter Motor Turns Slowly
Figure 111 (Sheet 1)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
 49-00-00
 ALL  ú
 ú  02  Page 150
 ú  Jul 12/00 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
　
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