(e) Do a continuity check between the IRS Mode Select Unit and IRS MCU:
IRS MSU IRS MCU CONNECTOR CONNECTOR D2171 D2269
pin19 -------------------pin12

(f)  If there is not continuity, then do these steps: 1) Repair the wiring. 2) Re-install the IRS Mode Select Unit. To install it, do this task: AMM
TASK 34-21-03-400-801. 3) Re-install the MMR. To install it, do this task: AMM TASK 34-31-42-400-801. 4) Re-install the IRS MCU. To install it, do this task: AMM TASK 34-21-07-400-801. 5) If the ILS light does not show on the IRS Mode Select Unit, then you corrected the fault.
-------------------------END OF TASK ---------------------------
820. ILS Light On When Master Caution Pushed -Fault Isolation
A.  Description
(1)  The ILS light shows on the IRS Mode Select Unit when the RECALL annunciator on the IRS Master Caution Unit is pushed.
B.  Possible Causes
(1)  
Multi-Mode Receiver (MMR-1), M2104 or (MMR-2), M2105.

(2)  
IRS Mode Select Unit, P5–69.

(3)  
IRS Master Caution Unit, M1206.

C.  Circuit Breakers
(1)  These are the primary circuit breakers related to the fault:
CAPT Electrical System Panel, P18-1
Row Col Number Name
A 2 C01479 RADIO NAVIGATION MMR 1

F/O Electrical System Panel, P6-1
Row Col Number Name
A 13 C01480 RADIO NAVIGATION MMR 2

EFFECTIVITY

34-31 TASKS 819-820
SIL ALL
Page 231 D633A103-SIL Jun 15/2010

D.  Related Data
(1)
(SSM 34-58-11).

(2)
(SSM 34-58-21).

(3)
(WDM 34-31-11).

(4)
(WDM 34-31-21).

(5)
(WDM 34-58-11).

(6)
(WDM 34-58-21).

E.  Initial Evaluation
(1)  Do
this
task:
ILS
or
Multi-Mode
Receiver
BITE
Procedure,
34-31
TASK
801

(a)  
If the ILS light shows on the IRS Mode Select Unit when the RECALL annunciator on the IRS Master Caution Unit is pushed, then do the Fault Isolation Procedure below.

(b)  
If the ILS light does not show on the IRS Mode Select Unit when the RECALL annunciator on the IRS Master Caution Unit is pushed, then there was an intermittent fault.

F. Fault Isolation Procedure
(1)  If LOC and G/S Flags are shown on either the Captain’s and F/O’s Displays, then do the appropriate task:
either
LOC
And
G/S
Flags
Show
On
The
Captain’s
Display
-Fault Isolation, 34-31 TASK 806, or
LOC
And
G/S
Flags
Show
On
The
F/O’s
Display
-Fault
Isolation,
34-31
TASK
807.

(a)  
If the ILS light does not show on the IRS Mode Select Unit when the RECALL annunciator on the IRS Master Caution Unit is pushed and LOC and G/S Flags does not shown on either the Captain’s and F/O’s Displays, then your corrected the fault.

(b)  
If the ILS light shows on the IRS Mode Select Unit when the RECALL annunciator on the IRS Master Caution Unit is pushed, then continue.

(2)
Replace the IRS Mode Select Unit, P5-69
These are the tasks:
AMM TASK 34-21-03-000-801,
AMM TASK 34-21-03-400-801.

(a)  
If the ILS light does not show on the IRS Mode Select Unit when the RECALL annunciator on the IRS Master Caution Unit is pushed, then you corrected the fault.

(b)  
If the ILS light shows on the IRS Mode Select Unit when the RECALL annunciator on the IRS Master Caution Unit is pushed, then continue.
　
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