The AVAIL Legend of the EXT PWR Pushbutton Switch Stays on when the Switch is Pushed

TASK 24-40-00-810-811-A
The AVAIL Legend of the EXT PWR Pushbutton Switch Stays on when the Switch is Pushed

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 24-22-33-000-001	Removal of the EGIU-1(2)
AMM 24-22-33-400-002	Installation of the EGIU-1(2)
ASM 242302
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
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)
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 24-40-00-710-060-A

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

NOTE: Energization of the aircraft is correct but, during the procedure given at Para. 3.E. and 3.F., make sure that:

on the ELEC panel 35VU, the AVAIL legend of the EXT PWR pushbutton switch stays on.

4. Fault Isolation
Subtask 24-40-00-810-060-A ** ON A/C NOT FOR ALL

A. If the test confirms the fault:

(1) If there is 28VDC:

(2) If there is not 28VDC:

do a check for ground signal at the pin A/X2 of the EPC AUX CTL relay ASM 244101.

(a) If there is a ground signal:

1 If the fault continues:

2 If the fault continues:

do a check and repair the wiring
. from the pin B/5 of the EPC to the first terminal block ASM 244101.
. from the pin B/3 of the EPC to the pin A/C1 of the EPC AUX CTL relay ASM 244101.
. from the pin A/C2 of the relay to the first terminal block ASM 242302.

(b) If there is no ground signal:

1 If the fault continues:

do a check and repair the wiring from the pin AB/3C of the EGIU1 (22XU1) to the pin A/X2 of the EPC AUX CTL relay ASM 244101.

Subtask 24-40-00-810-060-B ** ON A/C NOT FOR ALL

A. If the test confirms the fault:

(1) If there is 28VDC:

(2) If there is not 28VDC:

do a check for a ground signal at the pin A/X2 of the EPC auxiliary control relay (5XG) ASM 244101.

(a) If there is a ground signal:

1 If the fault continues:

2 If the fault continues:

do a check and repair the wiring between:
. the pin B/5 of the EPC (3XG) and the first terminal block ASM 244101
. the pin B/3 of the EPC and the pin A/C1 of the EPC auxiliary control relay (5XG) ASM 244101
. the pin A/C2 of the EPC auxiliary control relay and the first terminal block ASM 242302.

(b) If there is no ground signal:

1 If the fault continues:

do a check and repair the wiring between the pin AB/10A of the GAPCU (24XG) and the pin A/X2 of the EPC auxiliary control relay (5XG) ASM 244101.

Subtask 24-40-00-710-061-A

B. Do this test to make sure that the system operates correctly:
(1) Do the test given in Para. 3. and make sure that:

(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 04:26:53 UTC