Failure of the Ground Power Unit to Supply the Aircraft Electrical Circuits

TASK 24-41-00-810-833-A
Failure of the Ground Power Unit to Supply the Aircraft Electrical Circuits

1. Possible Causes

ground power unit

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 24-41-00-740-002	Operational Check of the GAPCU 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

3. Fault Confirmation
Subtask 24-41-00-710-075-A ** ON A/C NOT FOR ALL

A. If the Ground Power Unit (GPU) is connected to the aircraft electrical circuits while a different source supplies the aircraft electrical circuits (IDG, APU, batteries):

Disconnect the GPU from the external power receptacle (20XG).
On the ELEC panel 35VU, release, push and release again the ELEC/EXT PWR pushbutton switch (10XG) to do a reset of the GAPCU protection function.
Connect the GPU to the external power receptacle.

(1) If, on the EXT PWR panel 108VU, the EXT PWR/AVAIL caution light (9XG) comes on and if, on the ELEC panel 35VU, the AVAIL legend of the ELEC/EXT PWR pushbutton switch (10XG) comes on:

Stop the trouble shooting.

(2) If, on the EXT PWR panel 108VU, the EXT PWR/AVAIL caution light (9XG) stays off and if, on the ELEC panel 35VU, the AVAIL legend of the ELEC/EXT PWR pushbutton switch (10XG) stays off:

Do the trouble shooting given in Para. 4.A.

Subtask 24-41-00-710-076-A ** ON A/C NOT FOR ALL

B. If the Ground Power Unit (GPU) is connected to the aircraft electrical circuits with no other source(s) connected (IDG, APU, batteries):

Disconnect the GPU from the external power receptacle (20XG).
On the ELEC panel 35VU, push the BAT 1 and BAT 2 pushbutton switches (7PB1 and 7PB2) (on the MCDU menu page, make sure that the CFDS indication comes into view).
On the ELEC panel 35VU, release, push and release again the ELEC/EXT PWR pushbutton switch (10XG) to do a reset of the GAPCU protection function.
Connect the GPU to the external power receptacle.

(1) If, on the EXT PWR panel 108VU, the EXT PWR/AVAIL caution light (9XG) comes on and if, on the ELEC panel 35VU, the AVAIL legend of the ELEC/EXT PWR pushbutton switch (10XG) comes on:

Stop the trouble shooting.

(2) If, on the EXT PWR panel 108VU, the EXT PWR/AVAIL caution light (9XG) stays off and if, on the ELEC panel 35VU, the AVAIL legend of the ELEC/EXT PWR pushbutton switch (10XG) stays off:

Do the trouble shooting given in Para. 4.A.

4. Fault Isolation
Subtask 24-41-00-810-095-A ** ON A/C NOT FOR ALL

A. If the test confirms the fault:

Replace the ground power unit .

(1) If the fault continues:

Do the BITE test of the GAPCU AMM 24-41-00-740-002.

(a) If the BITE test gives fault messages:

Do the trouble shooting procedures related to the maintenance messages.

Subtask 24-41-00-860-073-A ** ON A/C NOT FOR ALL

B. Do this procedure to make sure that the system operates correctly.
(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 04:26:55 UTC