APU AUTO SHUTDOWN - NO ACCELERATION, Back-up Start Contactor Fault (131-9(A))

TASK 49-00-81-810-832-A
APU AUTO SHUTDOWN - NO ACCELERATION, Back-up Start Contactor Fault (131-9(A))

1. Possible Causes

BACKUP START CONTACTOR SHOWS OPEN CIRCUIT
FUSE-APU START [6KA]
CONTACTOR-BACK-UP START [10KA]
aircraft wiring
ELECTRONIC CONTROL BOX [59KD]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 49-00-00-860-008	APU Start by External Power
AMM 49-42-00-960-003	Replacement of the APU Start Fuse
ASM 494201
AMM 49-42-55-000-001	Removal of the Start Contactors
AMM 49-42-55-400-001	Installation of the Start Contactors
AMM 49-61-34-000-003	Removal of the Electronic Control Box (ECB) (131-9(A))
AMM 49-61-34-400-003	Installation of the Electronic Control Box (ECB) (131-9(A))

3. Fault Confirmation
Subtask 49-00-81-710-152-A ** ON A/C NOT FOR ALL

A. Read-out of ECB Trouble-Shooting Data
(1) Put the APU MASTER SW to the ON position.
(2) Get access to the APU SHUTDOWN report.
(3) Push the '>' adjacent to LRU DATA:

the MCDU menu shows
BACKUP START CONTACTOR SHOWS OPEN CIRCUIT

(4) Start the APU and apply Bleed Air for 20 seconds, minimum AMM 49-00-00-860-008.

4. Fault Isolation
Subtask 49-00-81-810-109-A ** ON A/C NOT FOR ALL

A. If an APU auto shutdown occurs during the APU operation and the APU SHUTDOWN report gives the maintenance message:

NO ACCELERATION
CONTACTOR (10KA)

associated with the Fault Code Number (FCN) 120

do a check for 28VDC at the BACK-UP START CONTACTOR (10KA) A/D ASM 494201.

(1) If there are not 28VDC:

replace the FUSE-APU START [6KA] AMM 49-42-00-960-003.

(2) If there are 28VDC:

replace the CONTACTOR-BACK-UP START [10KA] AMM 49-42-55-000-001 and AMM 49-42-55-400-001.

(a) If the fault continues:

do a check and repair of the aircraft wiring from
the BACK-UP START CONTACTOR (10KA) B/5 to GND
and
the BACK-UP START CONTACTOR (10KA) B/3 to the ECB (59KD) AC/6
and
the BACK-UP START CONTACTOR (10KA) A/G to the ECB (59KD) AB/E3 ASM 494201.
do a check for 28VDC at the BACK-UP START CONTACTOR (10KA) A/D ASM 494201.

(b) If the fault continues:

replace the ELECTRONIC CONTROL BOX [59KD] AMM 49-61-34-000-003 and AMM 49-61-34-400-003.

Subtask 49-00-81-710-153-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:34:34 UTC