Difference in Current between the APU GEN Current Transformer and the APU AC Current Transformer

TASK 24-23-00-810-802-A
Difference in Current between the APU GEN Current Transformer and the APU AC Current Transformer

1. Possible Causes

GCU-APU [1XS]
CT-AC, APU GEN [42XS]
wiring
GEN-APU [8XS]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
ASM 242301
AMM 24-23-17-000-001	Removal of the AC Current Transformer
AMM 24-23-17-400-001	Installation of the AC Current Transformer
AMM 24-23-34-000-001	Removal of the GCU-APU
AMM 24-23-34-400-001	Installation of the GCU-APU
AMM 24-23-51-000-001	Removal of the APU Generator
AMM 24-23-51-400-001	Installation of the APU Generator
AMM 24-41-00-740-004	Operational Check of the GPCU via the CFDS

3. Fault Confirmation
Subtask 24-23-00-710-051-A ** ON A/C NOT FOR ALL

A. Test
Do the operational test of the GPCU AMM 24-41-00-740-004.

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 24-23-00-810-051-A ** ON A/C NOT FOR ALL

A. If this test gives the maintenance message CHECK GCU APU PIN B11D, B13D:

Remove the APU GCU (1XS) AMM 24-23-34-000-001.
On the connector AB of the APU GCU (1XS), connect together the pins AB/13A to AB/13D ASM 242301.
Do an insulation check between the pins AB/13A to AB/13D of the connector AB of the APU GCU (1XS) and the ground.

(1) If the insulation check is correct:

On the connector AB of the APU GCU (1XS), disconnect the pins AB/13A to AB/13D and connect together the pins AB/11A to AB/11D ASM 242301.
Do an insulation check between the pins AB/11A to AB/11D and the ground.

(a) If the insulation check is correct:

Replace the GCU-APU [1XS] AMM 24-23-34-400-001.

(b) If the insulation check is not correct:

Disconnect the connector A of the APU-generator AC current-transformer (42XS).
Connect together the pins A/1 to A/4 of the APU-generator AC current-transformer (42XS) ASM 242301.
Do an insulation check between the pins A/1 to A/4 of the APU-generator AC current-transformer (42XS) and the ground.

1 If the insulation check is not correct:

Replace the CT-AC, APU GEN [42XS] AMM 24-23-17-000-001 and AMM 24-23-17-400-001.

2 If the insulation check is correct:

On the connector AB of the APU GCU (1XS), disconnect the pins AB/11A to AB/11D ASM 242301.

a Do an insulation check between:

The ground and, in sequence, the pins AB/11A to AB/11D of the connector AB of the APU GCU (1XS) and repair the wiring .

b Connect the connector A of the APU-generator AC current-transformer (42XS).
c Install the APU GCU (1XS) AMM 24-23-34-400-001.
(2) If the insulation check is not correct:

Disconnect the connector A of the APU generator (8XS).
On the APU generator (8XS), connect together the pins A/1 and A/6 to A/8 ASM 242301.
Do an insulation check between the pins A/1, A/6 to A/8 and the ground.

(a) If the insulation check is not correct:

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

(b) If the insulation check is correct:

Disconnect the pins AB/13A to AB/13D of the APU GCU (1XS) ASM 242301.

1 Do an insulation check between:

The ground and, in sequence, the pins AB/13A, AB/13B, AB/13C, AB/13D and repair the wiring .

2 Connect the connector A of the APU generator (8XS).
3 Install the APU GCU (1XS) AMM 24-23-34-400-001.

Subtask 24-23-00-710-052-A ** ON A/C NOT FOR ALL

B. After the subsequent flight, make sure that the fault does not continue.

[Rev.8 from Aug 2018] 2026.04.04 04:26:39 UTC