TM 9-2320-364-20-2 2-1366 24.  BLACKOUT DRIVE LIGHT DOES NOT OPERATE (CONT). Blackout marker lights operate   indicating 10 to 14 vdc to wire   1674. Blackout drive light lamp OK. Wire 1679 OK. Blackout drive light OK. Wire 1674 OK. BLACKOUT DRIVE switch   faulty. Wire 1679 faulty. KNOWN INFO POSSIBLE PROBLEMS TEST OPTIONS REASON FOR QUESTION Continuity test. STE/ICE-R #91. If continuity is not measured, BLACKOUT DRIVE switch is faulty.  If continuity is measured, wire 1679 is faulty. YES NO Replace BLACKOUT DRIVE switch (Para 7-27).   Verify repair, go to Step 6 of this Fault. 4. Is continuity measured on BLACKOUT DRIVE switch between terminals 5 and 1? Repair wire 1679 (see schematic Fig 2-35) or notify DS Maintenance.   Verify repair, go to Step 6 of this Fault. 3. Repair wire 1674 (see schematic Fig 2-35) or notify DS Maintenance.   Verify repair, go to Step 6 of this Fault. YES NO Blackout marker lights operate   indicating 10 to 14 vdc to wire   1674. Blackout drive light lamp OK. Wire 1679 OK. Black drive light OK. Wire 1674 faulty. BLACKOUT DRIVE switch   faulty. Wire 1679 faulty. KNOWN INFO POSSIBLE PROBLEMS TEST OPTIONS REASON FOR QUESTION Voltage test. STE/ICE-R #89. If wire 1674 is loose, faulty, or shorted to ground, blackout drive light will not operate. WARNING WARNING Are 10 to 14 vdc measured on wire 1674 at BLACKOUT DRIVE switch connector, terminal 5? Read WARNING on Page 2-1367 Read WARNING on Page 2-1367