Icing Indicator Lighting Inoperative

TASK 30-81-00-810-804-A
Icing Indicator Lighting Inoperative

1. Possible Causes

SW-INT LT/STBY COMPASS [2LF]
wiring from the circuit breaker (1LF) to the pin 1B of the ICE IND&/STBY COMPASS switch (2LF)
wiring from the lighted icing indicator (16DD) to the pin 2B of the ICE IND&/STBY COMPASS switch (2LF)
wiring between pin 1 of the lighted icing indicator (16DD) and pin 2B of the IC IND&/STBY COMPASS switch (2LF)
wiring between pin 2 of the lighted icing indicator (16DD) and the ground.

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AWM 308100
AMM 30-81-21-960-001	Replacement of the LED of the Lighted Icing Indicator
ASM 331300

3. Fault Confirmation
Subtask 30-81-00-710-056-A

A. On the INT LT section of the overhead control and indicating panel 25VU, set the ICE IND&/STBY COMPASS switch (2LF) to ON and make sure that the LED of the icing indicator does not come on.

4. Fault Isolation
Subtask 30-81-00-865-053-A

A. Table of the circuit breakers used in this procedure:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	LIGHTING/STBY/COMP/LIGHT	1LF	H04

Subtask 30-81-00-810-053-A

B. Make sure that the lighting of the standby compass is operative when the ICE IND&/STBY COMPASS switch (2LF) is in the ON position.
(1) If the lighting of the standby compass is inoperative, do a check of the circuit breaker (1LF) status.
(a) If the circuit breaker is closed:

Do a check for 28VDC at pin 2B of the ICE IND&/STBY COMPASS switch (2LF) ASM 331300.

1 If there is no 28VDC:

Do a check for 28VDC at pin 1B of the ICE IND&/STBY COMPASS switch (2LF) ASM 331300.

a If there is 28VDC:

Replace the SW-INT LT/STBY COMPASS [2LF] .

b If there is no 28VDC:

Do a check and repair the wiring from the circuit breaker (1LF) to the pin 1B of the ICE IND&/STBY COMPASS switch (2LF).

2 If there is 28VDC:

Do a check and repair the wiring from the lighted icing indicator (16DD) to the pin 2B of the ICE IND&/STBY COMPASS switch (2LF) AWM 308100.

(2) If the lighting of the standby compass is operative:
(a) Do a check for 28VDC at pin 1 of the lighted icing indicator (16DD)

If there is no 28VDC:

1 Do a check and repair the wiring between pin 1 of the lighted icing indicator (16DD) and pin 2B of the IC IND&/STBY COMPASS switch (2LF)

If there is 28VDC:

2 Do a check for a ground signal at pin 2 of the lighted icing indicator (16DD)
a If there is no ground signal:

Do a check and repair the wiring between pin 2 of the lighted icing indicator (16DD) and the ground.

b If there is a ground signal:

Replace the LED of the lighted icing indicator (16DD) AMM 30-81-21-960-001.

Subtask 30-81-00-710-057-A

C. On the INT LT section of the overhead control and indicating panel 25VU, set the ICE IND&/STBY COMPASS switch (2LF) to ON and make sure that the LED of the icing indicator comes on.

[Rev.8 from Aug 2018] 2026.04.04 04:29:47 UTC