Failure of the External Power Feeders and External Power POR-Wiring

TASK 24-41-00-810-823-A
Failure of the External Power Feeders and External Power POR-Wiring

1. Possible Causes

GAPCU [24XG]
feeders
wiring
external power

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
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 24-41-00-710-072-A ** ON A/C NOT FOR ALL

A. Test
(1) Energize the aircraft electrical circuits from the external power AMM 24-41-00-861-002.

4. Fault Isolation
Subtask 24-41-00-810-066-B ** ON A/C NOT FOR ALL

A. If it is not possible to connect the external power source to the aircraft electrical network and if the fault symptom is identified by the CFDS message WRG: EXT PWR FEEDER/WRG: POR + GAPCU (24XG):

stop the external power source,
disconnect the plug from the external power receptacle (20XG),
make sure that the APU generator is stopped and all the power sources to the GAPCU (28VDC backup power included) are removed,
replace the GAPCU [24XG] AMM 24-41-34-000-001 and AMM 24-41-34-400-001.

(1) If the fault continues:

do a check of the external power feeders ASM 244101 for a correct phase connection between:
. terminal A of the external power receptacle (20XG) and terminal K of the EPC (3XG)
. terminal B of the external power receptacle and terminal L of the EPC
. terminal C of the external power receptacle and terminal M of the EPC.

(a) If the feeders are not correct:

connect the feeders as necessary to get the correct phase sequence.

(b) If the feeders are correct:

do a check of the Point-Of-Regulation (POR) sense wiring ASM 244101 for a correct phase connection between:
. terminal J of the EPC (3XG) and pin B/15J of the GAPCU (phase A)
. terminal H of the EPC and pin B/14J of the GAPCU (phase B)
. terminal G of the EPC and pin B/13J of the GAPCU (phase C).

1 If the wiring is not correct:

connect the wiring as necessary to get the correct phase sequence.

2 If the wiring is correct and the fault continues:

replace the external power source.

Subtask 24-41-00-860-052-A ** ON A/C NOT FOR ALL

B. Make sure that the aircraft electrical circuits operate correctly in external power 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.

[Rev.8 from Aug 2018] 2026.04.04 04:26:54 UTC