Failure of the AC Current Transformer of the APU Generator or its Wiring

TASK 24-23-00-810-814-A
Failure of the AC Current Transformer of the APU Generator or its Wiring

1. Possible Causes

GEN-APU [8XS]
wiring
GAPCU [24XG]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
ASM 242301
AMM 24-23-51-000-001	Removal of the APU Generator
AMM 24-23-51-400-001	Installation of the APU Generator
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 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)

3. Fault Confirmation
Subtask 24-23-00-869-053-A ** ON A/C NOT FOR ALL

A. Test
Not applicable.

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

4. Fault Isolation

CAUTION: BEFORE YOU START THE CHECK OF IDG WIRING THAT INCLUDES CONNECTORS, EXAMINE EACH CONNECTOR TO MAKE SURE THAT THERE IS NO CONTAMINATION IN IT. IF YOU FIND CONTAMINATION, CLEAN THE CONNECTOR AND CONNECT IT AGAIN. IF THE FAILURE CONTINUES, DO THE TROUBLE SHOOTING PROCEDURE AS GIVEN BELOW.

Subtask 24-23-00-810-060-A ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the CFDS message GEN APU (8XS) GEN CT/ GAPCU (24XG) and the upper ECAM-DU warning APU GEN FAULT:

do an electrical resistance test of the APU generator AC current transformer ASM 242301 between:
. pins A/6 and A/1 of the APU generator (24.10 ohms plus or minus 2.41 ohms)
. pins A/7 and A/1 of the APU generator (24.10 ohms plus or minus 2.41 ohms)
. pins A/8 and A/1 of the APU generator (24.10 ohms plus or minus 2.41 ohms)
. pins A/6, A/7 and A/8 of the APU generator and APU generator case.

(1) If the resistance values are out of the specified limits:

replace the GEN-APU [8XS] AMM 24-23-51-000-001 and AMM 24-23-51-400-001.

(2) If the resistance values are in the specified limits:

do a check of the wiring ASM 242301 for a short to ground, a short circuit or an open circuit between:
. pin A/1 of the APU generator and pin A/14E of the GAPCU
. pin A/6 of the APU generator and pin A/14D of the GAPCU
. pin A/7 of the APU generator and pin A/15E of the GAPCU
. pin A/8 of the APU generator and pin A/15D of the GAPCU.

(a) If the wiring is not correct:

repair or replace as necessary.

(b) If the wiring is correct:

replace the GAPCU [24XG] AMM 24-41-34-000-001 and AMM 24-41-34-400-001.

1 If the fault continues:

replace the GEN-APU [8XS] AMM 24-23-51-000-001 and AMM 24-23-51-400-001.

Subtask 24-23-00-860-055-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) Let the APU generator operate for five minutes to make sure that it operates correctly.
(3) De-energize the aircraft electrical circuits from the APU AMM 24-41-00-862-002.

[Rev.8 from Aug 2018] 2026.04.04 04:26:40 UTC