Failure of the Auxiliary Power Unit Generator

TASK 24-20-00-810-948-A
Failure of the Auxiliary Power Unit Generator

1. Possible Causes

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

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
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 24-20-00-710-143-A ** ON A/C NOT FOR ALL

A. Test

NOTE: This CFDS message comes into view when there is an overfrequency trip condition of the APU generator related to an overspeed condition of the turbine. The CFDS message ECB (59KD)/APU (4005KM)/GAPCU (24XG) can come into view with CMS messages related to the chapter 49 or to the ECB. Do the trouble shooting procedure related to the chapter 49 or to the ECB messages before you do the trouble shooting for the CFDS message ECB (59KD)/APU (4005KM)/GAPCU (24XG).

(1) If the CFDS message ECB (59KD)APU (4005KM)/GAPCU (24XG) comes into view with CFDS messages related to the chapter 49 or to the ECB:

do the trouble shooting procedure related to the chapter 49 or ECB messages.

(2) If there are no chapter 49 or ECB messages, or if the fault continues after the trouble shooting:

do the trouble shooting given in Para 4.A.

4. Fault Isolation
Subtask 24-20-00-810-180-A ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the CFDS message ECB (59KD)/APU (4005KM)/GAPCU (24XG) and the upper ECAM-DU warning APU GEN FAULT:

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 24-20-00-860-173-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 04:26:26 UTC