Loss of the Bus Output from the FDU of the APU to the CFDIU

TASK 31-32-00-810-816-A
Loss of the Bus Output from the FDU of the APU to the CFDIU

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
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)
AMM 31-32-00-869-002	Procedure for the Class 3 Fault Reading
ASM 313206
AMM 31-32-34-000-001	Removal of the CFDIU
AMM 31-32-34-400-001	Installation of the CFDIU

3. Fault Confirmation
Subtask 31-32-00-865-063-A

A. Make sure that this(these) circuit breaker(s) is(are) closed:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
121VU	APU/FIRE AND OVHT/DET/LOOP B	2WG	L44
121VU	APU/FIRE AND OVHT/DET/LOOP A	1WG	L43

Subtask 31-32-00-740-078-A

B. On the CFDS MENU page, get access to the AVIONICS STATUS page AMM 31-32-00-869-002.

4. Fault Isolation
Subtask 31-32-00-810-064-A

A. If the test gives the maintenance message NO FDU APU DATA:

(1) If the fault continues:

(a) If the fault continues:

do a check and repair the wiring from CFDIU (1TW) to the FDU of the APU (13WG) from pins AA/2D, 2E to pins A/G, F , ASM 313206.

Subtask 31-32-00-740-079-A

B. Do the test given in Para. 3.B.

[Rev.8 from Aug 2018] 2026.04.04 04:29:49 UTC