Failure of the APU Availability Relay

TASK 24-20-00-810-836-A
Failure of the APU Availability Relay

1. Possible Causes

RELAY-APU AVAIL [6KD]
wiring
GCU-APU [1XS]
ELECTRONIC CONTROL BOX [59KD]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
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 24-41-00-861-002	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
ASM 496101
AMM 49-61-34-000-001	Removal of the Electronic Control Box (ECB) (GTCP 36-300)
AMM 49-61-34-400-001	Installation of the Electronic Control Box (ECB) (GTCP 36-300)

3. Fault Confirmation
Subtask 24-20-00-700-076-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 24-20-00-810-075-A ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the CFDS message CHECK GCU APU PIN A6A APU CTL RLY 6KD CKT and the upper ECAM DU warning APU GEN FAULT:

replace the RELAY-APU AVAIL [6KD] .

(1) If the fault continues:

do a check of the wiring for open circuit:
. between the APU generator pin B/2B and the APU availability relay pin A/2,
. then between the APU GCU pin A/6A and the APU availability relay pin A/1,
. then between the APU relay pin A/X1 and the ECB pin B/J6 ASM 242302 and ASM 496101.

(a) If the wiring is not correct:

repair the above defective wiring.

(b) If the wiring is correct:

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

replace the ELECTRONIC CONTROL BOX [59KD] AMM 49-61-34-000-001 and AMM 49-61-34-400-001.

Subtask 24-20-00-700-077-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