Failure of the APU Generator PMG

TASK 24-20-00-810-842-A
Failure of the APU Generator PMG

1. Possible Causes

wiring
GEN-APU [8XS]
GCU-APU [1XS]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
ASM 242301
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 24-41-00-861-002	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 24-20-00-700-088-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
Subtask 24-20-00-810-081-A ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the CFDS message CHECK GCU APU PIN C2 TO C4 GEN APU PIN A12 TO A14 and the upper ECAM DU warning APU GEN FAULT:

Do a check of the wiring for open circuit or short to ground between respectively the APU GEN pins A/12, A/13, A/14 and the APU GCU pins C/2, C/3, C/4 ASM 242301.

(1) If the wiring is not correct:

repair it.

(2) If the wiring is correct:

Do an impedance check of the APU generator PMG stator, between successively 2 among the 3 pins A/12, A/13 and A/14, then do a check for open circuit between the APU generator pins A/12, A/13, A/14 and the case.

NOTE: The normal impedance between 2 pins is 0.868 ohms plus or minus 0.156 ohms at 20°C.

(a) If the 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.

(b) If the values are in the specified limits:

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

Subtask 24-20-00-700-089-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-energize 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