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A12454
////////////////////////
A / GTCP85-129 SERIES /
737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 4 (BLOCK 31)
YES
YES32 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?

THE ELECTRONIC SPEED SWITCH,
S634, CONNECTOR D1245,
PINS C,D (WDM 49-31-01).

ARE THE CIRCUITS OK?

YES
YES

34 DO A CONTINUITY CHECK AT
THE ELECTRONIC SPEED SWITCH,
S634, CONNECTOR D1245,
PINS C AND D (WDM 49-31-01).

IS THERE AN OPEN CIRCUIT?

NO
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, M28O (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 110 (Sheet 5)

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 49-00-00
 PART NUMBER 305593  ú ú 02 Page 142 ú Jul 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
F11368
FROM SHEET 4 (BLOCK 8)
NO
36 EXAMINE THE CIRCUIT FROM
THE START RELAY, R5, TERMINAL
A2, TO THE STARTER MOTOR,
M161, POSITIVE TERMINAL
(WDM 49-31-01).

 IS THE CIRCUIT OK?
YES
NO
YES
NO
38 EXAMINE THE CIRCUIT FROM
THE START RELAY, R5, TERMINAL
X2, TO GROUND (WDM 49-31-01).
 IS THE CIRCUIT OK?

YES

Starter Motor Does Not Turn
Figure 110 (Sheet 6)

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 49-00-00
 PART NUMBER 305593  ú
 ú  02  Page 143
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A12460
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
PREREQUISITES 
MAKE SURE THIS SYSTEM WILL OPERATE: APU (AMM 49-11-00/201)
NOT TURN STARTER MOTOR DOES  MAKE SURE THE AIRPLANE IS IN THIS CONFIGURATION: ELECTRICAL POWER IS ON (AMM 24-22-00/201) 

POSSIBLE CAUSES:
1.STARTER MOTOR, M161, PROBLEM (AMM 49-41-11/401)
2.
START RELAY, R5, PROBLEM (WDM 49-31-01)

3.
ELECTRONIC SPEED SWITCH, S634, PROBLEM (AMM 49-61-22/401)

4.
APU CONTROL UNIT, M280, PROBLEM (AMM 49-61-11/401)

5.
APU MASTER SWITCH, S248, PROBLEM (WDM 49-31-01).

FAULT ISOLATION:
NO

1 MAKE SURE THE POSITIVE
LEAD AND NEGATIVE LEAD FOR THE
STARTER MOTOR ARE INSTALLED ON
THE CORRECT STARTER MOTOR

TERMINALS.
ARE THE LEADS FOR THE STARTER MOTOR CORRECTLY INSTALLED?

YES NO

2 MOVE THE APU MASTER SWITCH
52 MOVE THE APU MASTER SWITCH TO THE "ON" POSITION. TO THE "OFF" POSITION. DID THE AIR INLET DOOR DO THIS PROCEDURE: THE FULLY OPEN?AIR INLET DOOR DOES NOT FULLYOPEN (FIG. 108).

YES NO
3 MOVE THE APU MASTER SWITCH
TO THE "OFF" POSITION.
 DISCONNECT THE NEGATIVE LEAD FROM THE STARTER MOTOR.

EXAMINE THE NEGATIVE LEAD TO GROUND (WDM 49-31-01).
 IS THE CIRCUIT OK?

YES SEE SHEET 2
(BLOCK 4)

Starter Motor Does Not Turn
Figure 110A (Sheet 1)

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 49-00-00
 PART NUMBER 3876259  ú
 ú  02  Page 144
 ú  Jul 12/01 

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