TM 10-3930-669-20 12.  CAB LIGHT(S) DOES NOT OPERATE (CONT). KNOWN INFO TEST OPTIONS 24 vdc circuits operate. Fuse 10 OK. Wire 36 OK. Continuity test. STE/ICE-R #91. POSSIBLE PROBLEMS REASON FOR QUESTION Light wire 36 faulty. Light ground wire faulty. Lamp faulty If   continuity   is   not   present, lamp is faulty. KNOWN INFO TEST OPTIONS 24 vdc circuits operate. Lamp OK. Fuse 10 OK. Wire 36 OK. Voltage test. STE/ICE-R #89. POSSIBLE PROBLEMS REASON FOR QUESTION Light wire 36 faulty. Light ground wire faulty. If    22    to    24    vdc    are    not present,    light    wire    36    is faulty.  If light wire 36 is OK, light ground wire is faulty. 2-190