(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 GLS light does not show on the IRS Mode Select Unit, then you corrected the fault.
-------------------------END OF TASK ---------------------------
822. GLS Light On When Master Caution Pushed -Fault Isolation
A.  Description
(1)  If the GLS light shows on the IRS Mode Select Unit when the RECALL annunciator on the IRS Master Caution Unit is pushed.
B.  Possible Causes
(1)  
GPS antenna connection (M2102), D2947 or (M2103), D2941.

(2)  
Multi-Mode Receiver (MMR-1), M2104 or (MMR-2), M2105.

(3)  
IRS Mode Select Unit, P5–69.

(4)  
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

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).

EFFECTIVITY

34-31 TASKS 821-822
SIL ALL
Page 236 D633A103-SIL Jun 15/2010

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

(a)  
If the GLS 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 GLS 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 both or either the Captain’s and F/O’s Displays, then do these tasks:
LOC
And
G/S
Flags
Show
On
The
Captain’s
Display
-Fault
Isolation,
34-31
TASK
806
and/or
LOC
And
G/S
Flags
Show
On
The
F/O’s
Display
-Fault
Isolation,
34-31
TASK
807.

(a)  
If the GLS 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 the Captain’s and/or F/O’s Displays, then you corrected the fault

(b)  
If the GLS light shows on the IRS Mode Select Unit when the RECALL annunciator on the IRS Master Caution Unit is pushed and LOC and G/S Flags shown on the Captain’s and/or F/O’s Displays, then continue.

(2)  Do the inspection of the GPS antenna connection.
(a)  Check for any loose GPS cable connections between the MMR and the GPS antenna:
MMR E1-2 CONNECTOR CONNECTOR D10719A D42941P
pin2 -------------------pinA1
E1-2 GPS ANTENNA CONNECTOR CONNECTOR D42941J D2941
A1  ---------------------A1
MMR E1-4 CONNECTOR CONNECTOR D10721A D42943P
pin2 -------------------pinA1
E1-4 GPS ANTENNA CONNECTOR CONNECTOR D42943J D2947
　
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