Aircraft Electrical Circuits cannot be supplied from the External Power

TASK 24-41-00-810-809-A
Aircraft Electrical Circuits cannot be supplied from the External Power

1. Possible Causes

RCPT-EXT PWR [20XG]
EPC [3XG]
GLC-APU [3XS]
RELAY-EPC AUX CTL [5XG]
GLC-1 [9XU1]
GLC-2 [9XU2]
wiring

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 24-22-55-000-001	Removal of the Contactors
AMM 24-22-55-400-002	Installation of the Contactors
AMM 24-23-55-000-001	Removal of the APU GLC
AMM 24-23-55-400-001	Installation of the APU GLC
AMM 24-41-00-861-002	Energize the Aircraft Electrical Circuits from the External Power
ASM 244101
AMM 24-41-51-000-001	Removal of the External Power Receptacle
AMM 24-41-51-400-001	Installation of the External Power Receptacle
AMM 24-41-55-000-001	Removal of the External Power Contactor (EPC)
AMM 24-41-55-400-001	Installation of the External Power Contactor (EPC)

3. Fault Confirmation
Subtask 24-41-00-710-066-A

A. Energize the Aircraft Electrical Circuits from the External Power AMM 24-41-00-861-002.

NOTE: Examine the external power supply-cable and the external power receptacle before you do the connection.
If you find corrosion or damage, or if the pins are not aligned correctly, replace the RCPT-EXT PWR [20XG] AMM 24-41-51-000-001 and AMM 24-41-51-400-001.

4. Fault Isolation
Subtask 24-41-00-810-058-A

A. If the above procedure confirms the results below when the EXT PWR pushbutton switch is pushed:
. the AVAIL legend of the EXT PWR pushbutton switch stays on,
. the ON legend of the EXT PWR pushbutton switch does not come on,
. the FAULT legend of the GEN1 and the GEN2 pushbutton switches stays off.

Do a check for 28VDC between pins B/3 and B/5 of the EPC (3XG) ASM 244101.

(1) If there is 28VDC:

Replace the EPC [3XG] AMM 24-41-55-000-001 and AMM 24-41-55-400-001.

(2) If there is no 28VDC:

Do a check for 28VDC at pins A/D1 then A/X1 of the EPC auxiliary control relay (5XG).

(a) If there is 28VDC:

Do a check for 28VDC at pin B/24 of the APU GLC (3XS) ASM 244101.

1 If there is 28VDC:

Replace the GLC-APU [3XS] AMM 24-23-55-000-001 and AMM 24-23-55-400-001.

2 If there is no 28VDC:

Replace the RELAY-EPC AUX CTL [5XG] .

3 If the fault continues:

Do a check of the wiring between pins B/10 and B/12 of the GLC1 and of the GLC2.

a If there is no continuity:

Replace the GLC-1 [9XU1] and/or GLC-2 [9XU2] AMM 24-22-55-000-001 and AMM 24-22-55-400-002.

b If there is continuity:

Do a check and repair the wiring between pin B/3 of the EPC (3XG) and pin A/D2 of the EPC auxiliary control relay (5XG) ASM 244101.

(b) If there is no 28VDC:

Do a check and repair the wiring between pins A/D1 and A/X1 of the EPC auxiliary control relay (5XG) and the circuit breaker (11XG) ASM 244101.

Subtask 24-41-00-710-067-A

B. Do the procedure given in Para 3.A.

[Rev.8 from Aug 2018] 2026.04.04 04:26:53 UTC