Failure of the APU FDU

TASK 26-13-00-810-813-A
Failure of the APU FDU

1. Possible Causes

FDU-APU [13WG]
WIRING

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 26-13-00-710-002	BITE Test of the APU Fire and Overheat Detection System
ASM 261301
AMM 26-13-34-000-001	Removal of the APU Fire-Detection Unit (FDU)
AMM 26-13-34-400-001	Installation of the APU Fire-Detection Unit (FDU)

3. Fault Confirmation
Subtask 26-13-00-740-050-A

A. Do the Bite test of the APU fire and overheat detection system AMM 26-13-00-710-002.

4. Fault Isolation
Subtask 26-13-00-810-075-A

A. If the Bite test gives a maintenance message different from FDU APU:

Do the trouble-shooting procedure related to the maintenance message.

Subtask 26-13-00-810-076-A

B. If the Bite test gives the maintenance message FDU APU:

Replace the FDU-APU [13WG] AMM 26-13-34-000-001 AMM 26-13-34-400-001.

Subtask 26-13-00-740-051-A

C. Do the test given in Para. 3.

Subtask 26-13-00-810-077-A

D. If the fault continues:
(1) Do a check and repair the WIRING between:
(a) FDU-APU [13WG] connector A pin A and CB (1WG),
(b) FDU-APU [13WG] connector B pin A and CB (2WG),
(c) FDU-APU [13WG] connector A pin B and GND,
(d) FDU-APU [13WG] connector B pin N and GND,
(e) FDU-APU [13WG] connector B pin B and GND.
ASM 261301

5. Close-up
Subtask 26-13-00-860-055-A

A. Put the aircraft back to its initial configuration.
(1) Make sure that the work area is clean and clear of tools and other items.

[Rev.8 from Aug 2018] 2026.04.04 04:27:17 UTC