CAPTAIN'S HSI CAPTAIN'S ADI FMC-CDU
FMCS SENSOR S
LRU LEFTVHF NAV
DME OK
CAPTAIN'S RDDMI F/O'S RDDMI
ILS TEST PREPARATION ILS TEST PROCEDURE (DOWN/RIGHT) FMC-CDU
ILS Self-Test Pictorial
Figure 17

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
 1.

2.

3.

A
737-300/400/500MAINTENANCE MANUAL
 VOR/ILS NAVIGATION SYSTEM - TROUBLESHOOTING
___________________________________________
General
_______
 A.  The troubleshooting for the VOR/ILS navigation system is almost the same as the self-test for system No. 1. The difference is that the troubleshooting procedure contains corrective actions. To do the troubleshooting procedure for system No. 2 use this procedure but replace these items in the procedure:
 (1)
The captain's instruments with the first officer's instruments

 (2)
The narrow pointers with the wide pointers

 (3)
The narrow pointer flags with the wide pointer flags.

 B.  The procedure is in a step by step format. The steps show the OK and NOT OK condition path. When all steps in the OK condition path are correct, the system is OK.
 C.  When a step is NOT OK, follow the NOT OK line to the step that contains the symptom. Do the corrective action for the symptom, then do the step that was NOT OK again.
 D.  It is necessary that the wire bundles are OK and that electrical power is available to do the troubleshooting procedure. If the corrective action does not correct the problem, use the wiring diagrams to make sure the wires are OK.
Standard Tools and Equipment
____________________________
 A.  VOR/ILS Ramp Test Set - 972Q-4, Collins, Cedar Rapid, Iowa, or NAV-401L,
 Instrument & Flight Research Inc, Witchita, KS.Troubleshooting Tips
____________________
 A.  Make sure that power to the defective system is available.
 B.  Malfunctions of the VOR/ILS navigation system can be divided into four groups:
 (1)
VOR/LOC deviation

 (2)
Glide slope deviation

 (3)
VOR bearing

 (4)
Warnings.

 C.  If warnings show in the indicators, use the VHF NAV transfer switch to isolate the defective component.
 D.  If the VOR bearing displays are different when the two systems are tuned to the same station, replace the navigation units. If the problem continues, examine the coaxial cables at the VOR/LOC antenna for corrosion, loose connectors, and/or damage.
 NOTE: A ground station signal that is nonsymmetrical can cause different
____ bearing and deviation displays when tuned to the same frequency.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
 4.  Prepare for the Troubleshooting
_______________________________
 A.  Make sure that all applicable circuit breakers on panels P6 and P18 are closed:
 (1)
VOR/ILS

 (2)
IRS

 (3)
DAA

 (4)
Flight Instrument

 (5)
Instrument Transfer.

 B.  Supply electrical power (Ref 24-22-00/201).
 C.  Set the ATTITUDE, the COMPASS, and the VHF NAV transfer switches (P1 panel) to the NORMAL position.
 NOTE: During the troubleshooting procedure, NORMAL position of a
____ transfer switch is the captain on 1 and the first officer on 2.
 D.  Set the ADF/VOR switches on the RDDMIs (P1 and P3 panels) to the VOR position.
 E.  Set the HSI transfer switches (P7 panel) to the VOR/ILS position.
 (1) Make sure the source annunciators on the HSIs show VOR/ILS.
　
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