APU Start Switch ON Legend inoperative (131-9(A))

TASK 49-00-81-810-898-A
APU Start Switch ON Legend inoperative (131-9(A))

1. Possible Causes

bulbs
aircraft wiring
ELECTRONIC CONTROL BOX [59KD]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 33-14-00-810-801-A	Failure of One Annunciator Light Only
AMM 33-14-00-710-001	Operational Test of the Lights
ASM 494201
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 49-00-81-710-246-A ** ON A/C NOT FOR ALL

A. Test
(1) Release the BAT1 and BAT2 p/bsw to the OFF position.
(2) Push the APU Master SW p/bsw and wait until the air-intake flap is in the open position.
(3) Push the APU Start SW p/bsw and check that the ON legend comes on.
(4) Release the APU Master SW p/bsw.
(5) Push the BAT1 and BAT2 p/bsw to the ON position.

4. Fault Isolation
Subtask 49-00-81-810-163-A ** ON A/C NOT FOR ALL

A. If the ON legend is off:

do the Operational Test of the Annunciator Light Test System in the Cockpit AMM 33-14-00-710-001.

(1) If the fault continues:

replace the bulbs .

(a) If the fault continues:
(Ref. TSM TASK 33-14-00-810-801).
(2) If the Annunciator Light Test is OK:

check and repair the aircraft wiring between ECB (59KD) AB/H9 and RELAY BOARD (7LP) A/15 ASM 494201.

(a) If the fault continues:

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

Subtask 49-00-81-710-247-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:34:39 UTC