YES
NO

22 MOVE THE APU MASTER SWITCH
TO THE "OFF" POSITION.
 DISCONNECT THE ELECTRICAL CONNECTOR D1245, FROM THE ELECTRONIC SPEED SWITCH, S634.
 MEASURE THE RESISTANCE AT THE ELECTRONIC SPEED SWITCH, S634, CONNECTOR D1245, FROM PINS, F TO M, K TO L(WDM 40-31-01).
 THE RESISTANCE MUST BE LESS THAN 100 OHMS.
MEASURE THE RESISTANCE AT THE ELECTRONIC SPEED SWITCH, S634, CONNECTOR D1245, FROM PINS, C TO D, J TO M, L TO E (WDM 49-31-01).
THE RESISTANCE MUST BEMORE THAN 1000K OHMS.
ARE THE RESISTANCES VALUES IN THE RANGE SPECIFIED?

YES
NO

23 CONNECT THE ELECTRICAL
CONNECTOR D1254, TO THE
ELECTRONIC SPEED SWITCH, S634.
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

24 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
NO
25 MEASURE THE RESISTANCE AT
THE SURGE BLEED VALVE,
CONNECTOR D1584, FROM PIN 1

TO PIN 2 (WDM 49-31-01).
 IS THE RESISTANCE 25-60 OHMS?

YES
SEE SHEET 3 (BLOCK 26)
Circuit Breaker on the APU Control Unit Opens during the APU Operation
Figure 109A (Sheet 2)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 3876259  ú
 ú  02  Page 132
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
L37257
////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 2 (BLOCK 25)

YES
YES
26 MEASURE THE RESISTANCE AT THE 3-WAY SOLENOID VALVE,
CONNECTOR D1574, FROM PIN A TO PIN B (WDM 49-31-01).
IS THE RESISTANCE 35-110 OHMS?
NO
YES
27 EXAMINE THE CIRCUIT FROM THE ELECTRONIC SPEED SWITCH
(95% SWITCH; 110% SWITCH), S634, CONNECTOR D1245,
PINS, J, E, TO THE APU CONTROL UNIT, M280, CONNECTOR D50B,
PINS, 32, 35 (WDM 49-31-01). IS THERE A SHORT CIRCUIT?
NO
YES
28 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
YES29 EXAMINE THE CIRCUIT FROM
THE FUEL SOLENOID VALVE TO
THE APU CONTROL UNIT, M280
(WDM 49-31-01, WDM 49-41-01).
IS THERE A SHORT CIRCUIT?

NO
YES
30 EXAMINE THE CIRCUIT FROM
THE SURGE BLEED VALVE TO THE
APU CONTROL UNIT, M280

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

NO
YES
31 EXAMINE THE CIRCUIT FROM
THE HOURMETER TO THE APU
CONTROL UNIT, M280

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

Circuit Breaker on the APU Control Unit
Opens during the APU Operation
Figure 109A (Sheet 3)

L37541
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
 PART NUMBER 3876259  ú
 ú  02  Page 133
 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 1 (BLOCK 1)
YES

NO
NO

32 MOVE THE APU MASTER SWITCH TO THE "OFF" POSITION. DISCONNECT THE ELECTRICAL

YES
SEE SHEET 7 (BLOCK 44)
CONNECTOR D1245, FROM THEELECTRONIC SPEED SWITCH, S634.
MEASURE THE RESISTANCE AT THE ELECTRONIC SPEED SWITCH,S634, CONNECTOR D1245, FROM PINS, F TO M, K TO L (WDM 40-31-01).
THE RESISTANCE MUST BE LESS THAN 100 OHMS.
MEASURE THE RESISTANCE AT THE ELECTRONIC SPEED SWITCH,S634, CONNECTOR D1245, FROM PINS, C TO D, J TO M, L TO E (WDM 49-31-01).
THE RESISTANCE MUST BE MORE THAN 1000K OHMS.
ARE THE RESISTANCES VALUESIN THE RANGE SPECIFIED?

YES
NO
33 MEASURE THE RESISTANCE AT THE SEQUENCING PRESSURE SWITCH FOR THE OIL, CONNECTOR D1250, FROM PIN 3 TO PIN 4 (WDM 49-31-01).
　
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