BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
FROM SHEET 1 (BLOCK 1)
YES NO NO

33 MOVE THE APU MASTER SWITCH
TO THE "OFF" POSITION. MEASURE THE RESISTANCE AT
THE ELECTRONIC SPEED SWITCH,
YES S634, CONNECTOR D1245, FROM
PINS C TO D, J TO M, K TO L
SEE SHEET 7 (WDM 49-31-01).
(BLOCK 47) ARE THE RESISTANCES

0-1 OHMS (MAXIMUM)? YES

NO

34 MEASURE THE RESISTANCE AT THE ELECTRONIC SPEED SWITCH, S634, CONNECTOR D1245, FROMPIN G TO PIN H (WDM 49-31-01).

IS THE RESISTANCE 4000-6000 OHMS?

YES NO
35 MEASURE THE RESISTANCE AT THE ELECTRONIC SPEED SWITCH, S634, CONNECTOR D1245, FROM PINS A TO G, M TO F, L TO E, B TO G (WDM 49-31-01).

ARE THE RESISTANCES A MINIMUM OF 1000K OHMS?

YESNO
36 MEASURE THE RESISTANCE AT THE SEQUENCING PRESSURE SWITCHFOR THE OIL, CONNECTOR D1250, FROM PIN 3 TO PIN 4 (WDM 49-31-01).

IS THE RESISTANCE MORE THAN 1000K OHMS?

YES NO
37 MEASURE THE RESISTANCE AT THE FUEL SOLENOID VALVE, CONNECTOR D1264, FROM PIN A TO PIN B (WDM 49-31-01).

IS THE RESISTANCE 20-45 OHMS?
YES SEE SHEET 5 (BLOCK 38)
Circuit Breaker on the APU Control Unit
Opens during the APU Operation
Figure 109 (Sheet 4)

A11980
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 49-00-00
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 ú  03  Page 127
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 4 (BLOCK 37)

YES
NO
38 MEASURE THE RESISTANCE AT
THE IGNITION UNIT, CONNECTOR
D1256, FROM PIN A TO CASE AND

PIN B TO CASE (WDM 49-31-01).
ARE THE RESISTANCES A MINIMUM OF 1000K OHMS?

YES
NO
39 MEASURE THE RESISTANCE
BETWEEN EACH SOCKET OF THE
CONNECTOR FOR THE IGNITER

CABLE.
 ARE THE RESISTANCES 0-0.1 OHMS (MAXIMUM)?

YES
NO
40 MEASURE THE RESISTANCE
BETWEEN EACH SOCKET AND THE
CASE OF THE CONNECTOR FOR THE

IGNITER CABLE.
 ARE THE RESISTANCES AMINIMUM OF 1000K OHMS?

YES
YES
41 EXAMINE THE CIRCUIT FROM
THE ELECTRONIC SPEED SWITCH
TO THE APU CONTROL UNIT, M280

(WDM 49-31-01).
 IS THERE A SHORT CIRCUIT?

NO
YES
42 EXAMINE THE CIRCUIT FROM
THE SEQUENCING PRESSURE SWITCH
FOR THE OIL TO THE APU CONTROL

UNIT, M280 (WDM 49-31-01).
 IS THERE A SHORT CIRCUIT?

NO
SEE SHEET 6 (BLOCK 43)
Circuit Breaker on the APU Control Unit
Opens during the APU Operation
Figure 109 (Sheet 5)

E05849
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
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 ú  03  Page 128
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
FROM SHEET 5 (BLOCK 42)

NO
YES

43 EXAMINE THE CIRCUIT FROM
THE FUEL SOLENOID VALVE TO
THE APU CONTROL UNIT, M280
(WDM 49-31-01; 49-41-01).

IS THERE A SHORT CIRCUIT?

NO
YES
44 EXAMINE THE CIRCUIT FROM
THE IGNITION UNIT TO THE APU
CONTROL UNIT, M280
(WDM 49-31-01).

IS THERE A SHORT CIRCUIT?

IS THE APU HARNESS OK? YES

Circuit Breaker on the APU Control Unit
Opens during the APU Operation
Figure 109 (Sheet 6)

E05853
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
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 ú  02  Page 129
 ú  Jul 12/01 

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