Failure of the Generator Control Unit 2

TASK 24-20-00-810-881-A
Failure of the Generator Control Unit 2

1. Possible Causes

GCU-2 [1XU2]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 24-22-34-000-001	Removal of the GCU-1(2)
AMM 24-22-34-400-001	Installation of the GCU-1(2)
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
AMM 31-60-00-860-001	EIS Start Procedure
AMM 31-60-00-860-002	EIS Stop Procedure
AMM 71-00-00-710-003	Engine Automatic Start
AMM 71-00-00-710-028	Engine Shutdown
AMM 71-00-00-860-814	Shutdown of the Engine
AMM 71-00-00-860-823	Start the Engine (Normal Automatic Start)

3. Fault Confirmation
Subtask 24-20-00-740-076-A ** ON A/C NOT FOR ALL

A. Test
(1) Remove all AC and DC power from the GCU 2:

de-energize the aircraft electrical circuits from the APU AMM 24-41-00-862-002,
de-energize the aircraft electrical circuits from the external power AMM 24-41-00-862-002,
disconnect the batteries or open the GCU 2 circuit breaker (2XU2) to remove the 28VDC backup power-supply from the GCU 2.

(2) Apply power to the GCU 2:

energize the aircraft electrical circuits from the APU AMM 24-41-00-861-002,
energize the aircraft electrical circuits from the external power AMM 24-41-00-861-002.

(3) Do the BITE test of the GAPCU AMM 24-41-00-740-002.
(a) If the BITE test gives the message TEST FAILED:

push the line key adjacent to the TEST FAILED message.

1 If the maintenance message GCU2 (1XU2) comes into view:

do the trouble shooting procedure given in Para 4.A.

(b) If the BITE test gives the message TEST PASSED:

stop the trouble shooting.

4. Fault Isolation
Subtask 24-20-00-810-169-A ** ON A/C NOT FOR ALL

A. If the BITE test gives the maintenance message GCU2 (1XU2) or if the APU generator or the external power do not energize the aircraft electrical circuits:

replace the GCU-2 [1XU2] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

Subtask 24-20-00-710-155-C ** ON A/C NOT FOR ALL

B. Do this operational test to make sure that the system operates correctly.
(1) Aircraft Maintenance Configuration
(a) Energize the aircraft electrical circuits
AMM 24-41-00-861-002.
(b) Do the EIS start procedure (Upper ECAM DU and lower ECAM DU only)
AMM 31-60-00-860-001.
(2) In the cockpit, on the ELEC panel 35VU:

Push, release and push again the GEN 2 pushbutton switch (3XU2).

(3) Do the BITE test of the GAPCU AMM 24-41-00-740-002.
(4) Start engine 2 AMM 71-00-00-860-823.
(5) Do this test:

ACTION	RESULT
On the ECAM control panel: Push the ELEC key to get the ELEC page.	On the lower ECAM DU: The correct electrical parameters of GEN 2 are shown and GEN 2 supplies the AC2 busbar.

Subtask 24-20-00-710-155-F ** ON A/C NOT FOR ALL

push, release and push again the GEN 2 pushbutton switch (3XU2).

(3) Do the operational test of the GAPCU AMM 24-41-00-740-002.
(4) Start the engine 2 AMM 71-00-00-710-003.
(5) Do this test:

ACTION	RESULT
On the ECAM control panel: get the ELEC page.	On the lower ECAM DU: the correct electrical parameters of the GEN 2 are shown and the AC2 busbar is supplied by the GEN 2.

5. Close-up
Subtask 24-20-00-860-189-C ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) Stop engine 2 AMM 71-00-00-860-814.
(2) Do the EIS stop procedure
AMM 31-60-00-860-002.
(3) On the ECAM control panel, set the UPPER DISPLAY and LOWER DISPLAY potentiometers to OFF.
(4) De-energize the aircraft electrical circuits
AMM 24-41-00-862-002.

Subtask 24-20-00-860-189-F ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) Stop the engine 2 AMM 71-00-00-710-028.
(2) Do the EIS stop procedure
AMM 31-60-00-860-002.
(3) On the ECAM control panel, set the UPPER DISPLAY and LOWER DISPLAY potentiometers to OFF.
(4) De-energize the aircraft electrical circuits
AMM 24-41-00-862-002.

[Rev.8 from Aug 2018] 2026.04.04 04:26:17 UTC