Standby Compass Lighting Failure

TASK 33-13-00-810-804-A
Standby Compass Lighting Failure

1. Possible Causes

SW-INT LT/STBY COMPASS [2LF]
wiring from the circuit breaker (1LF) to the STBY COMPASS switch (2LF)
COMPASS-STANDBY [2FN]
wiring from the standby compass (2FN) to the STBY COMPASS switch (2LF)
C/B-LIGHTING/STBY/COMP/LIGHT [1LF]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 24-00-00-810-803-A	Circuit Breaker Tripped and/or C/B TRIPPED Warning
ASM 331302
AIPC 331308
AMM 34-22-00-710-001	Operational Check of the standby compass including light test and visual check
AMM 34-22-23-000-001	Removal of the Standby Compass
AMM 34-22-23-400-001	Installation of the Standby Compass

3. Fault Confirmation
Subtask 33-13-00-710-056-A

A. Do the operational test of the standby compass AMM 34-22-00-710-001.

4. Fault Isolation
Subtask 33-13-00-810-053-A

A. If during the operational test, when the INT LT/STBY COMPASS switch (2LF) is in the STBY COMPASS position, the lighting of the standby compass is inoperative:

do a check of the circuit breaker (1LF) status.

(1) If the circuit breaker is closed:

do a check for 28VDC at pin 2B of the standby compass switch (2LF) ASM 331302.

(a) If there is no 28VDC:

replace the SW-INT LT/STBY COMPASS [2LF] AIPC 331308.

1 If the fault continues:

do a check and repair the wiring from the circuit breaker (1LF) to the STBY COMPASS switch (2LF) pin 1B ASM 331302.

(b) If there is 28VDC:

replace the COMPASS-STANDBY [2FN] AMM 34-22-23-000-001 and AMM 34-22-23-400-001.

1 If the fault continues:

do a check and repair the wiring from the standby compass (2FN) to the STBY COMPASS switch (2LF) pin 2B ASM 331302.

(2) If the circuit breaker is open:

do the procedure (Ref. TSM TASK 24-00-00-810-803).

(a) If the circuit breaker stays closed and the fault continues:

replace the C/B-LIGHTING/STBY/COMP/LIGHT [1LF] .

Subtask 33-13-00-710-057-A

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:31:54 UTC