F. Fault Isolation Procedure
(1)
Replace the applicable ADIRU.
These are the tasks:
Air Data Inertial Reference Unit Removal, AMM TASK 34-21-01-000-801,
Air Data Inertial Reference Unit Installation, AMM TASK 34-21-01-400-801.

(a)  
Do a check of the condition of the pins and connector of the applicable ADIRU.

(b)  
If the maintenance message does not show on the CDU, and the status code does not show on the ISDU, then you corrected the fault.

(c)  
If the maintenance message does show on the CDU, and the status code does show on the ISDU, then continue.

(2)  
Do this check of the wiring for the applicable ADIRU:

(a)  
Remove the ADIRU. To remove it, do this task: Air Data Inertial Reference Unit Removal, AMM TASK 34-21-01-000-801.

(b)  
For the left ADIRU, do a wiring check between these pins of connectors: 1) Do a wiring check between these pins of connectors D3687A and D3687B:

D3687A  D3687B
pinA9 -----------------pinK4 pinB9 -----------------pinK5

(c)  For the right ADIRU, do a wiring check between these pins of connectors: 1) Do a wiring check between these pins of connector D3693A and D3693B:
D3693A  D3693B
pinA9 -----------------pinK4 pinB9 -----------------pinK5

(d)  If you find a problem with the wiring, then do these steps: 1) Repair the wiring. 2) Re-install the ADIRU. To install it, do this task: Air Data Inertial Reference Unit
Installation, AMM TASK 34-21-01-400-801. 3) For
the
applicable
ADIRS,
do
this
task:
ADIRS
BITE
Procedure,
34-21
TASK
801.
4) If the maintenance message does not show on the CDU and the status code does not
show on the ISDU, then you corrected the fault.
-------------------------END OF TASK ---------------------------
EFFECTIVITY SIL ALL  34-21 TASK 841 
D633A103-SIL BOEING PROPRIETARY -Copyright # Unpublished Work -See title page for details  Page 278 Oct 15/2008 

842.  IRS DC FAIL ANNUNCIATOR LIGHT -Fault Isolation
A.  Description
(1)  
This task is for IRS DC FAIL LIGHT

(2)  
The left IRS DC FAIL LIGHT is shown on the left side of the MSU. The right IRS DC FAIL LIGHT is shown on the right side of the MSU.

B.  Possible Causes
(1)
Wiring problem

(2)  
IFSAU

(3)  
ADIRU

(4)  
Mode Select Unit (MSU)

C.  Circuit Breakers
(1)  These are the primary circuit breakers related to the fault:
CAPT Electrical System Panel, P18-1
Row Col Number Name
E 5 C01009 ADIRU LEFT DC
E 7 C01007 ADIRU LEFT AC

CAPT Electrical System Panel, P18-2
Row Col Number Name
E 8 C00425 ADIRU LEFT EXC

F/O Electrical System Panel, P6-1
Row Col Number Name
C 14 C01008 ADIRU RIGHT AC
C 15 C00426 ADIRU RIGHT EXC
C 17 C01010 ADIRU RIGHT DC

D.  Related Data
(1)
(SSM 34-21).

(2)
(WDM 34-21).

E.  Initial Evaluation
(1) Flight Crew reported the IRS DC FAIL light illuminating during flight.
F. Fault Isolation Procedure
(1)  Do this check for 28v dc power signal:
(a)  
Remove the ADIRU. To remove it, do this task: Air Data Inertial Reference Unit Removal, AMM TASK 34-21-01-000-801

(b)  
For the left ADIRU:
1) Remove the safety tag and close this circuit breaker:

CAPT Electrical System Panel, P18-1 Row Col Number Name E 5 C01009 ADIRU LEFT DC
　
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