Failure of EPSU 10WL

TASK 33-51-00-810-822-A
Failure of EPSU 10WL

1. Possible Causes

POWER-EMERGENCY SUPPLY [10WL]
signs and lights
wiring

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 33-51-00-710-001	Operational Test of the Emergency Lights
ASM 335101
ASM 335104
AMM 33-51-38-000-001	Removal of the Emergency Power-Supply Unit (EPSU)
AMM 33-51-38-400-001	Installation of the Emergency Power-Supply Unit (EPSU)

3. Fault Confirmation

CAUTION: DO NOT USE THE TEACH-IN PROCEDURE AS AN ALTERNATIVE FOR TROUBLESHOOTING. A TEACH-IN PROCEDURE IS NOT A RESET PROCEDURE. BEFORE YOU DO A TEACH-IN PROCEDURE, MAKE SURE THAT YOU CORRECTED ALL FAILURES. IF YOU DO NOT OBEY THIS, FAILURES CAN CAUSE A MALFUNCTION OF THE CABIN EMERGENCY LIGHTING SYSTEM.

Subtask 33-51-00-710-085-A ** ON A/C NOT FOR ALL

A. Do the operational test of the emergency lights with the MCDU AMM 33-51-00-710-001.

4. Fault Isolation
Subtask 33-51-00-810-093-A ** ON A/C NOT FOR ALL

A. If the test gives a different maintenance message, do the trouble shooting procedure related to the maintenance message.

Subtask 33-51-00-810-094-A ** ON A/C NOT FOR ALL

B. If the operational test gives the maintenance message:
EPSU(10WL)FWD L:

replace the POWER-EMERGENCY SUPPLY [10WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(1) If the fault continues:

check all connected signs and lights for a short-circuit and replace if necessary ASM 335101 and ASM 335104,
if you find one or more defective signs and lights, replace the POWER-EMERGENCY SUPPLY [10WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(2) If the fault continues:

do a check for a short to ground and repair the wiring if necessary ASM 335101 and ASM 335104:
from EPSU (10WL) pin E to the connector(s) of the related signs and lights,
from EPSU (10WL) pin F to the connector(s) of the related signs and lights,
from EPSU (10WL) pin G to the connector(s) of the related signs and lights,
from EPSU (10WL) pin H to the connector(s) of the related signs and lights,
from EPSU (10WL) pin J to the connector(s) of the related signs and lights,
from EPSU (10WL) pin N to the connector(s) of the related signs and lights,
from EPSU (10WL) pin R to the connector(s) of the related signs and lights,
from EPSU (10WL) pin T to the connector(s) of the related signs and lights,
from EPSU (10WL) pin -B to the connector(s) of the related signs and lights,
from EPSU (10WL) pin -C to the connector(s) of the related signs and lights,
from EPSU (10WL) pin -H to the connector(s) of the related signs and lights,
from EPSU (10WL) pin -J to the connector(s) of the related signs and lights,
if you find a short to ground in the wiring, replace the POWER-EMERGENCY SUPPLY [10WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(3) If the fault continues:

do a check and repair the wiring if necessary ASM 335101:
from EPSU (10WL) pin -I to DEU-B (300RH1) pin B/29,
from EPSU (10WL) pin -P to DEU-B (300RH1) pin B/31,
from EPSU (10WL) pin X to DEU-B (300RH1) pin B/30,
from EPSU (10WL) pin L to GND,
from EPSU (10WL) pin M to GND,
from EPSU (10WL) pin U to GND,
from EPSU (10WL) pin -R to GND,
from EPSU (10WL) pin -M to GND.

Subtask 33-51-00-710-086-A ** ON A/C NOT FOR ALL

C. Do the test given in Para. 3.

5. Close-up
Subtask 33-51-00-860-076-A ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.

[Rev.8 from Aug 2018] 2026.04.04 04:32:09 UTC