SPEED (FIG. 136) AUTOMATIC SHUTDOWN FOR A LOW OIL PRES-SURE OR THE "LOW OIL PRESSURE" LIGHT STAYS ON AND THE APU ENGINE STOPS APPROXIMATELY 10 SECONDS AFTER 100%
OR "FAULT" LIGHT IS ON (FIG. 137) AUTOMATIC SHUTDOWN - "HIGH OIL TEMP"
IS ON (FIG. 138) AUTOMATIC SHUTDOWN - "OVERSPEED" LIGHT
WARNING INDICATION (FIG. 139) AUTOMATIC/MANUAL SHUTDOWN - FIRE
(FIG. 140) AUTOMATIC SHUTDOWN - NO APPARENT CAUSE
IS ON (FIG. 141) APU USUAL SHUTDOWN - "OVERSPEED" LIGHT
Fault Index
Figure 101 (Sheet 3)
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
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PREREQUISITES
"OVERSPEED" LIGHT MAKE SURE THIS SYSTEM WILL OPERATE:
IS ON WHEN THE APU APU (AMM 49-11-00/201)
MASTER SWITCH IS IN MAKE SURE THE AIRPLANE IS IN THIS CONFIGURATION:
THE "OFF" POSITION ELECTRICAL POWER IS ON (AMM 24-22-00/201)
POSSIBLE CAUSES:
1.PILOT STOPPED THE APU DURING STARTUP.
2.
ELECTRONIC SPEED SWITCH, S634, PROBLEM (AMM 49-61-22/401)
3.
APU CONTROL UNIT, M280, PROBLEM (AMM 49-61-11/401)
4.
TACHOMETER GENERATOR (AMM 49-61-61/401)
5.
FUEL CONTROL UNIT PROBLEM (AMM 49-31-11/401)
6.
APU INTERNAL DAMAGE (AMM 49-11-00/401).
FAULT ISOLATION:
YES YES
1 MOVE THE APU MASTER SWITCH
21 START THE APU
TO THE "ON" POSITION. (AMM 49-11-00/201).
DOES THE "OVERSPEED" DID THE APU START AND
LIGHT GO OFF? OPERATE CORRECTLY?
NO
NO
NO
2 MOVE THE APU MASTER SWITCH
TO THE "OFF" POSITION.
FOR AN APU CONTROL UNIT
WITH THE TEST LIGHTS:
MOMENTARILY PUSH THE
"OVERSPEED RESET/TEST" SWITCH
ON THE APU CONTROL UNIT.
DOES THE "TEST PASS" LIGHT
COME ON?
FOR AN APU CONTROL UNIT
WITHOUT THE TEST LIGHTS:
MOMENTARILY PUSH THE
"OVERSPEED RESET" SWITCH ON
THE APU CONTROL UNIT.
DOES THE "OVERSPEED"
LIGHT GO OFF?
YES SEE SHEET 2
(BLOCK 3)
OVERSPEED Light Is On when the APU Master Switch Is in the OFF Position
Figure 102 (Sheet 1)
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////////////////////////A / GTCP85-129 SERIES /737-300/400/500/ ENGINES /MAINTENANCE MANUAL ////////////////////////
FROM SHEET 1
(BLOCK 2)
YES
YES YES
3
START AND OPERATE THE APU
22 LET THE APU OPERATE FOR
(AMM 49-11-00/201). 5 MINUTES.
DID THE APU START AND DO THE APU USUAL SHUTDOWN OPERATE CORRECTLY? (AMM 49-11-00/201).
DID THE "OVERSPEED" LIGHT
NO
COME ON?
NO
NO
4 EXAMINE THE CIRCUIT FROM
THE ELECTRONIC SPEED SWITCH,
S634, CONNECTOR D1245, PIN E,
TO THE APU CONTROL UNIT, M280,
CONNECTOR D50B, PIN 35
(WDM 49-31-01).
IS THE CIRCUIT OK?
YES NO5 REPLACE THE ELECTRONIC
SPEED SWITCH (AMM 49-61-22/
401).
START AND OPERATE THE APU (AMM 49-11-00/201).
DID THE APU HAVE AN"OVERSPEED" SHUTDOWN?
YES
SEE SHEET 3 (BLOCK 6)
OVERSPEED Light Is On When the APU Master Switch Is in the OFF Position
Figure 102 (Sheet 2)
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