TM 10-3930-669-20 7.  TAILLIGHTS, FRONT LIGHT, GAUGE LIGHTS, AND MAST LIGHT DO NOT OPERATE (CONT). KNOWN INFO Cab interior lights operate. Fuse 6 OK. POSSIBLE PROBLEMS Wire 25A faulty. Front light switch faulty. KNOWN INFO Cab interior lights operate. Fuse 6 OK. Wire 25A OK. POSSIBLE PROBLEMS Front light switch faulty. TEST OPTIONS Voltage test. STE/ICE-R #89. REASON FOR QUESTION If 22 to 24 vdc are not present , wire 25A is faulty. TEST OPTIONS Continuity test. STE/ICE-R #91. REASON FOR QUESTION If continuity is not present , switch is faulty. ¬ ¬ 2-164