Contactor (5KA) Fault (131-9(A))

TASK 49-40-00-810-807-A
Contactor (5KA) Fault (131-9(A))

1. Possible Causes

MAIN START CONTACTOR SHOWS CLOSED
CONTACTOR-MAIN START [5KA]
ELECTRONIC CONTROL BOX [59KD]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 49-00-00-710-010	Operational Test of the APU
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 49-40-00-710-062-A ** ON A/C NOT FOR ALL

A. Read-out of the ECB Trouble Shooting Data
(1) Get access to the APU LAST LEG/PREVIOUS LEG report.
(2) Push the '>' adjacent to the related CFDS failure message:

the MCDU menu shows:
MAIN START CONTACTOR SHOWS CLOSED

(3) Put the APU MASTER SW to the ON position.
(4) Get access to the APU GND SCANNING menu.

4. Fault Isolation
Subtask 49-40-00-810-056-A ** ON A/C NOT FOR ALL

A. If the APU GND SCANNING menu gives the maintenance message:

CONTACTOR (5KA)

associated with Fault Code Number (FCN) 124

replace the CONTACTOR-MAIN START [5KA] AMM 49-42-55-000-001 and AMM 49-42-55-400-001.

(1) If fault continues after the first flight on the subsequent day:

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

Subtask 49-40-00-710-063-A ** ON A/C NOT FOR ALL

B. Do the operational test of the APU AMM 49-00-00-710-010.

NOTE: Make an entry in the applicable lokbook that you must read the APU CLASS 3 FAULTS after the first flight on the subsequent day.

[Rev.8 from Aug 2018] 2026.04.04 04:34:40 UTC