EPSU - 115 VAC Fault Message

TASK 33-51-00-810-804-A
EPSU - 115 VAC Fault Message

1. Possible Causes

POWER-EMERGENCY SUPPLY [10WL]
wiring
EPSU [11WL]
EPSU [12WL]
EPSU [13WL]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 33-51-00-710-001	Operational Test of the Emergency Lights
ASM 335101
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 33-51-00-710-056-A ** ON A/C NOT FOR ALL

A. Test
(1) Do the operational test of the emergency lighting system AMM 33-51-00-710-001.

4. Fault Isolation
Subtask 33-51-00-810-053-A ** ON A/C NOT FOR ALL

A. If the operational test gives the maintenance message:
(1) EPSU 115 VAC FWD L:

do a check for 115 VAC at the POWER SUPPLY UNIT-EMERGENCY (10WL) pin K.

(a) If there is 115 VAC:

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

(b) If there is no 115 VAC:

do a check and repair the wiring between:
POWER SUPPLY UNIT-EMERGENCY (10WL) pin K and CB 3WL,
POWER SUPPLY UNIT-EMERGENCY (10WL) pin M and GND ASM 335101.

(2) EPSU 115 VAC EMER L:

do a check for 115 VAC at POWER SUPPLY UNIT-EMERGENCY (11WL) pin K.

(a) If there is 115 VAC:

replace the EPSU [11WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(b) If there is no 115 VAC:

do a check and repair the wiring between:
POWER SUPPLY UNIT-EMERGENCY (11WL) pin K and CB 3WL,
POWER SUPPLY UNIT-EMERGENCY (11WL) pin M and GND ASM 335101.

(3) EPSU 115 VAC EMER R:

do a check for 115 VAC at
POWER SUPPLY UNIT-EMERGENCY (12WL) pin K.

(a) If there is 115 VAC:

replace the EPSU [12WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(b) If there is no 115 VAC:

do a check and repair the wiring between:
POWER SUPPLY UNIT-EMERGENCY (12WL) pin K and CB 3WL,
POWER SUPPLY UNIT-EMERGENCY (12WL) pin M and GND ASM 335101.

(4) EPSU 115 VAC AFT L:

do a check for 115 VAC at POWER SUPPLY UNIT-EMERGENCY (13WL) pin K.

(a) If there is 115 VAC:

replace the
EPSU [13WL] AMM 33-51-38-000-001 and AMM 33-51-38-400-001.

(b) If there is no 115 VAC:

do a check and repair the wiring between:
POWER SUPPLY UNIT-EMERGENCY (13WL) pin K and CB 3WL,
POWER SUPPLY UNIT-EMERGENCY (13WL) pin M and GND ASM 335101.

Subtask 33-51-00-710-057-A ** ON A/C NOT FOR ALL

B. Do the test as given in the Para. 3.A.

5. Close-up
Subtask 33-51-00-860-067-A ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.

[Rev.8 from Aug 2018] 2026.04.04 04:32:07 UTC