NO

21 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 ATTHE 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 VALUES IN THE RANGE SPECIFIED?
YES
NO

22 CONNECT THE ELECTRICAL
CONNECTOR D1254, TO THE
ELECTONIC SPEED SWITCH, S634.
MEASURE THE RESISTANCE AT THE SEQUENCING PRESSURE SWITCH FOR THE OIL, CONNECTOR D1250, FROM PIN 3 TO PIN 4 (WDM 49-31-01).
IS THE RESISTANCE MORE THAN 1000K OHMS?

YES
SEE SHEET 3 (BLOCK 23)
APU Engine Speed Decreases
Figure 125A (Sheet 2)

L37742
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. APU WITH THE ELECTRONIC SPEED SWITCH ú
 49-00-00
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 ú  02  Page 182
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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FROM SHEET 2 (BLOCK 22)

YES
NO

23 MEASURE THE RESISTANCE AT
THE FUEL SOLENOID VALVE,
CONNECTOR D1264, FROM PIN A
TO PIN B (WDM 49-31-01).
ARE THE RESISTANCES 20-45 OHMS?
YES
NO

24 DO A CHECK FOR THE
INTERMITTENT ELECTRICAL SIGNAL
AT THE ELECTRONIC SPEED SWITCH
(110% SWITCH), S634, CONNECTOR

D1245, PIN E (WDM 49-31-01).
IS THE ELECTRICAL SIGNAL TO PIN E CONTINUOUS AND STRONG?

YES
NO

25 DO A CHECK FOR THE
INTERMITTENT ELECTRICAL SIGNAL
AT THE SEQUENCING PRESSURE
SWITCH FOR THE OIL, CONNECTOR

D1250, PIN 3 (WDM 49-31-01).
IS THE ELECTRICAL SIGNAL TO PIN 3 CONTINUOUS AND STRONG?

YES
NO

26 DO A CHECK FOR THE
INTERMITTENT ELECTRICAL SIGNAL
AT THE FUEL SOLENOID VALVE,
CONNECTOR D1264, PIN A
(WDM 49-31-01).
IS THE ELECTRICAL SIGNAL YESTO PIN A CONTINUOUS AND STRONG?

APU Engine Speed Decreases
Figure 125A (Sheet 3)

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 49-00-00
 PART NUMBER 3876259  ú
 ú  02  Page 182A
 ú  Jul 12/01 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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PREREQUISITES
MAKE SURE THESE SYSTEMS WILL OPERATE:

PRESSURE IN THE BLEED
PNEUMATIC (AMM 36-05-00/201)
AIR DUCT IS NOT
APU (AMM 49-11-00/201)
CONSTANT DURING THE
MAKE SURE THE AIRPLANE IS IN THIS CONFIGURATION:
MAIN ENGINE START
ELECTRICAL POWER IS ON (AMM 24-22-00/201)

POSSIBLE CAUSES:
1.
3-WAY SOLENOID VALVE PROBLEM (AMM 49-52-61/401)

2.
LEAKAGE FROM THE BLEED AIR DUCT

3.
BLEED AIR VALVE, V56, PROBLEM (AMM 49-52-11/401)

4.
CLOGGED FILTER FOR THE DIFFERENTIAL PRESSURE REGULATOR (AMM 49-52-21/301)

5.
DIFFERENTIAL PRESSURE REGULATOR PROBLEM (AMM 49-52-21/401)

6.
FUEL CONTROL UNIT PROBLEM (AMM 49-31-11/401)

7.
CLOGGED FILTER ELEMENT FOR THE LOW-PRESSURE FUEL (AMM 49-31-22/401)

8.
CLOGGED FILTER FOR THE HIGH-PRESSURE FUEL (AMM 49-31-81/301)

9.
ELECTRONIC SPEED SWITCH, S634, PROBLEM (AMM 49-61-22/401)

10.
TACHOMETER GENERATOR PROBLEM (AMM 49-61-61/401)

11.
APU ELECTRICAL GENERATOR PROBLEM (AMM 24-21-21/401)

12.
APU INTERNAL DAMAGE (AMM 49-11-00/401).

FAULT ISOLATION:
NO

1 START THE APU
51 DO THIS PROCEDURE: "APU
(AMM 49-11-00/201). GEN OFF BUS" LIGHT DOES NOT
DID THE "APU GEN OFF COME ON WHEN THE APU ENGINEBUS" LIGHT COME ON WHEN THESPEED GETS TO 95% (FIG. 117). APU SPEED ACCELERATED TO 95%?
　
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