BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A13874
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 1 (BLOCK 2)

FROM THE IGNITION UNIT. START THE APU (AMM 49-11-00/201).
____ WITH THE CONNECTOR DIS-
NOTE: CONNECTED FROM THE IGNITION UNIT, THE APU WILL NOT START.
AFTER THE AIR INLET DOOR OPENS, DO A CHECK FOR VOLTAGEAT THE IGNITION UNIT, CONNEC-TOR D1256, PIN B (WDM 49-31-01).
IS THERE MORE THAN 11V DC AT PIN B?

NO
NO

5 MOVE THE APU MASTER SWITCH
TO THE "OFF" POSITION.

 EXAMINE THE CIRCUIT FROM THE IGNITION UNIT, CONNECTOR D1256, PIN B, TO THE ELEC-TRONIC SPEED SWITCH, S634, CONNECTOR D1245, PIN J (WDM 49-31-01).
IS THE CIRCUIT OK?

YES
SEE SHEET 3(BLOCK 6)
(AMM 49-41-31/401).

Starter Motor Turns the APU Engine but There Is No Combustion (No Increase in EGT)
Figure 113 (Sheet 2)

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 305593  ú
 ú  02  Page 154
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A13875
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 2 (BLOCK 5)

YES

YES
6
CONNECT CONNECTOR D1256
TO THE IGNITION UNIT.

DO A CONTINUITY CHECK AT THE ELECTRONIC SPEED SWITCH, S634, CONNECTOR D1245, PINS J TO M AND PINS K TO L (WDM 49-31-01).
IS THERE AN OPEN CIRCUIT?

NO NO
YES SEE SHEET 4 (BLOCK 8)
21 _______

WARNING
DO NOT OPERATE THE APU WITH THE LOWER SHROUD REMOVED IF PERSONS ARE IN OR DIRECTLY 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.
EXAMINE THE CIRCUIT FROMTHE APU CONTROL UNIT, M280, CONNECTOR D50B, PIN 4, TO THE ELECTRONIC SPEED SWITCH, S634, CONNECTOR D1245, PIN L (WDM 49-31-01).
IS THE CIRCUIT OK?
NO

PINS M,K, TO THE SEQUENCING SWITCH FOR THE OIL PRESSURE, CONNECTOR D1250, PINS 4,3(WDM 49-31-01).
ARE THE CIRCUITS OK?

YES SEE SHEET 4 (BLOCK 24)
Starter Motor Turns the APU Engine but There Is No Combustion (No Increase in EGT)
Figure 113 (Sheet 3)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 305593  ú
 ú  02  Page 155
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
F11405
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 3 FROM SHEET 3 (BLOCK 7) (BLOCK 23)

YES
YES YES
24 DO THE APU DRY MOTORING 59 REPLACE THE SEQUENCING (AMM 49-11-00/201).SWITCH FOR THE OIL PRESSURE
DURING THE APU DRY (AMM 49-61-41/401).
MOTORING, DO A CHECK OF THE
OIL PRESSURE.
 DID THE OIL PRESSURE INCREASE TO 4.0 PSIG
(27.6 kPa)?
NO

NONO

8 DISCONNECT CONNECTOR D1245
25 MOVE THE APU MASTER SWITCH
FROM THE ELECTRONIC SPEED TO THE "OFF" POSITION.
SWITCH. EXAMINE THE CIRCUIT FROM

MOVE THE APU MASTER SWITCH THE APU CONTROL UNIT, M280, TO THE "START" POSITION. CONNECTOR D50B, PIN 4, TO THE
AFTER THE AIR INLET DOOR ELECTRONIC SPEED SWITCH, S634, OPENS, DO A CHECK FOR VOLTAGE CONNECTOR D1245, PIN L AT THE ELECTRONIC SPEED (WDM 49-31-01).SWITCH, S634, CONNECTOR D1245, IS THE CIRCUIT OK? PIN L (WDM 49-31-01).
YES
IS THERE 28V DC AT PIN L?
62 CONNECT CONNECTOR D1245 TO

YES
THE ELECTRONIC SPEED SWITCH. REPLACE THE APU CONTROL UNIT, M280 (AMM 49-61-11/401).
NO

9 MOVE THE APU MASTER SWITCH
TO THE "OFF" POSITION.

EXAMINE THE CIRCUITS FROM THE ELECTRONIC SPEED SWITCH, S634, CONNECTOR D1245, PINS M,K, TO THE SEQUENCING SWITCH FOR THE OIL PRESSURE, CONNECTOR D1250, PINS 4,3 (WDM 49-31-01).
　
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