Failure of the Electrical Wiring between the APU GCU and the APU GLC

TASK 24-20-00-810-846-A
Failure of the Electrical Wiring between the APU GCU and the APU GLC

1. Possible Causes

wiring
GLC-APU [3XS]
RELAY-APU GLC AUX CTL [4XS]
GCU-APU [1XS]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 24-20-00-810-838-A	Failure of the Internal Circuit Breaker of the APU GCU
ASM 242302
AMM 24-23-34-000-001	Removal of the GCU-APU
AMM 24-23-34-400-001	Installation of the GCU-APU
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

3. Fault Confirmation
Subtask 24-20-00-700-108-A ** ON A/C NOT FOR ALL

A. Test
Not applicable.

NOTE: As the GEN APU was set to OFF because of a true failure, the fault confirmation is not necessary.

4. Fault Isolation
Subtask 24-20-00-810-097-A ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the CFDS message : CHECK GLC APU AND/OR CONTROL CKT and the warning APU GEN FAULT on the upper ECAM display unit:

do a check of the status of the APU GCU circuit breaker.

(1) If the circuit breaker is open:

refer to (Ref. TSM TASK 24-20-00-810-838).

(2) If the circuit breaker is closed:

do a check of the wiring between respectively:
. the pin B/2D of the APU GCU and the pin B/3 of the APU GLC, through relays (5XG, 4XS), BTC1, BTC2, GLC1, CLC2, EPC
. the pin B/2D and the pins A/12D, A/6A, A/13D of the APU GCU,
. the pin A/12C of the APU GCU and the pin X1 of the APU GLC auxiliary control relay (4XS), via the ELEC/APU GEN pushbutton switch (2XS),
. the pin X2 of the APU GLC auxiliary control relay and the ground,
. the pin B/5 of the APU GLC and the ground, ASM 242302.

(a) If the wiring is not correct:

repair it.

(b) If the wiring is correct:

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

replace the RELAY-APU GLC AUX CTL [4XS] .

(d) If the fault continues:

replace the GCU-APU [1XS] AMM 24-23-34-000-001 and AMM 24-23-34-400-001.

Subtask 24-20-00-700-109-A ** ON A/C NOT FOR ALL

B. Make sure that the aircraft electrical circuits operate correctly in APU configuration.
(1) Energize the aircraft electrical circuits from the APU AMM 24-41-00-861-002.
(2) De-energizee the aircraft electrical circuits from the APU AMM 24-41-00-862-002.

[Rev.8 from Aug 2018] 2026.04.04 04:26:13 UTC