TM 55-1520-240-T
CHAPTER 15
AUXILIARY POWER UNIT SYSTEM TROUBLESHOOTING
CHAPTER OVERVIEW
Chapter 15 contains procedures for Auxiliary Power Unit System troubleshooting. Each system and failure symptom is listed below.
Included in this chapter are locations and views of all electrical connectors, receptacles, relays, and ground connections for the Auxiliary
Power Unit System.
Refer to TM 55-1520-240-23 for required maintenance procedures.
SYSTEM
PARA
AUXILIARY POWER UNIT
15-1
FAILURE SYMPTOM LIST
AUXILIARY POWER UNIT
SYMPTOM
TASK
SYMPTOM
TASK
SYMPTOM
TASK
APU CONT NORM OR APU CONT EMERG CIRCUIT
BREAKER DOES NOT STAY CLOSED
15-1.4
APU DOES NOT MOTOR WHEN APU SWITCH IS
SET TO START (WITHOUT
15-1.4
APU DOES NOT MOTOR WHEN APU SWITCH IS
SET TO START (WITH
15-1.4
APU HAS HOT START
15-1.4
APU MOTORS BUT DOES NOT START, ESU BITE lN-
15-1.4
APU MOTORS BUT DOES NOT START, ESU BITE lN-
15-1.4
APU MOTORS BUT DOES NOT START; ESU BITE lN-
15-1.4
APU ON CAPSULE GOES OUT (APU SHUTS DOWN)
WHEN APU CONT CIRCUIT BREAKER OPENED
15-1.4
APU ON CAPSULE OUT WHEN APU OPERATING
NORMALLY
15-1.4
APU SHUTS DOWN DURING START, ESU BITE lNDl-
15-1,4
APU SHUTS DOWN WHEN APU GEN SWITCH IS
SET TO OFF
15-1.4
APU STARTS AND RUNS BUT ESU BITE INDICATES
15-1.4
APU STARTS BUT SHUTS DOWN, ESU BITE lNDl-
15-1.4
APU STARTS BUT SHUTS DOWN, ESU BITE lNDl-
15-1,4
APU STARTS BUT SHUTS DOWN, ESU BITE lNDl-
15-1.4
ESU BITE INDICATORS ARE NOT BLACK OR APU
FUEL BOOST PUMP CANNOT BE HEARD OPERATING
BEFORE APU SWITCH SET TO START
15-1.4
15-2.1
