TM 5-6675-250-10
3-2. TROUBLESHOOTING - Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
ELECTRONIC CONTROL UNIT (Continued)
Check for defective GRU.
Step 3.
a.
Replace existing GRU with a GRU that is operable. If the system
operates correctly with the new GRU, this indicates the original GRU
was defective.
b. Replace a defective GRU with a new one by disconnecting and
connecting power cables.
c. Report defective GRU to the next higher level of maintenance.
4. GYRO SYNC INDICATOR FAILS TO LIGHT WITHIN TWO MINUTES AFTER MODE SELECT SWITCH
IS PLACED TO GC.
Check for defective GYRO SYNC indicator lamp.
Step 1.
a. Unscrew the plastic lens from the indicator lamp assembly.
b. Visually inspect lamp for a burned out filament. If filament is defec-
tive, replace with a new lamp.
c. Place the new lamp in the socket of the lamp assembly. Screw the
plastic lens in place over the lamp and tighten the plastic lens finger
tight.
Check for defective ECU.
Step 2.
a. Place TEST SELECT switch in GYRO position; depress PRESS TO
TEST switch for a voltage indication.
b. Replace defective ECU with an ECU that is operable by disconnect-
ing and connecting power cables.
c. Report a defective ECU to next higher level of maintenance.
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