TM 10-3930-669-20 19.  GLOW PLUG INDICATOR DOES NOT OPERATE (CONT). KNOWN INFO 24 vdc circuits operate. Fuse 4 OK. Indicator wire 30 OK. Relay R6 ground wire OK. POSSIBLE PROBLEMS Indicator ground wire faulty. Wire 31 faulty. Terminal 85 ground wire faulty. Relay R6, wire 30, terminal 30 faulty. Relay R6, wire 30, terminal 87 faulty. Wire 29 faulty. Glow plug switch faulty. Wire 31 faulty. TEST OPTIONS Continuity test. STE/ICE-R #91. REASON FOR QUESTION If continuity is not present, connector is faulty.  If connector is OK, glow plug indicator is faulty. 2-234