Failure of the External Power Phase Sequence

TASK 24-40-00-810-801-A
Failure of the External Power Phase Sequence

1. Possible Causes

feeder wires
wiring
GPCU [1XG]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 24-41-00-740-004	Operational Check of the GPCU via the CFDS
AMM 24-41-00-861-002	Energize the Aircraft Electrical Circuits from the External Power
AMM 24-41-00-862-002	De-energize the Aircraft Electrical Circuits Supplied from the External Power
ASM 244101
AMM 24-41-34-000-001	Removal of the Ground Power Control Unit (GPCU)
AMM 24-41-34-400-001	Installation of the Ground Power Control Unit (GPCU)

3. Fault Confirmation
Subtask 24-40-00-860-050-A ** ON A/C NOT FOR ALL

A. Job Set-Up
(1) Aircraft Maintenance Configuration
(a) Energize the aircraft electrical circuits
AMM 24-41-00-861-002

Subtask 24-40-00-740-050-A ** ON A/C NOT FOR ALL

B. Test
Do the operational check of the GPCU with the CFDS AMM 24-41-00-740-004.

4. Fault Isolation
Subtask 24-40-00-810-050-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message CHECK EP PHASE SEQ and if on the overhead panel, on the panel 35VU, the AVAIL legend of the EXT PWR pushbutton switch is on:

do a check of the external power feeder wires for cross-connection between the pins A, B, C of the external power receptacle (20XG) and the pins A/K, A/L, A/M of the EPC ASM 244101.

(1) If the wiring is not correct:

repair it.

(2) If the wiring is correct:

replace the external power unit.

(3) If the fault continues:

do a check of the wiring for wire cross-connection between respectively the pins B/5C, B/6D, B/7C of the GPCU and the pins A/J, A/H, A/G of the EPC, through the GND PWR PROT circuit breaker (2XG) (Ref. ASM 2441/01).

(4) If the fault continues:

replace the GPCU [1XG] , AMM 24-41-34-000-001 and AMM 24-41-34-400-001.

Subtask 24-40-00-700-051-A ** ON A/C NOT FOR ALL

B. Make sure that the aircraft electrical circuits operate correctly in ground configuration.
(1) Energize the aircraft electrical circuits from the external power AMM 24-41-00-861-002.
(2) De-energize the aircraft electrical circuits from the external power AMM 24-41-00-862-002.

5. Close-up
Subtask 24-40-00-860-051-A ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) On the ECAM control panel, set the UPPER DISPLAY and LOWER DISPLAY potentiometers to OFF.
(2) De-energize the aircraft electrical circuits
AMM 24-41-00-862-002

[Rev.8 from Aug 2018] 2026.04.04 04:26:52 UTC