TM 9-2320-364-20-3 2-2918 6.  FAN SPEED DOES NOT LOWER FROM HIGH SPEED TO LOW SPEED (CONT). 7. Repair wire 1538 (see schematic Fig 2-67) or notify DS Maintenance. Verify repair, go to Step 19 of this Fault. YES NO Heater blower motor operates,   indicating CB15 OK. Fan operates at low speed with   hydraulic selector switch in   AUTO or CRANE/SRW   position. Fan operates at low speed with   throttle position switch   depressed. Wire 1933 between MC59 and   MC128 OK. Wire 1932 between MC59 and   MC61 OK. Wire 1932 between MC61 and   MC128 OK. Temperature sensor OK. Wire 1538 faulty. Wire 1435 from fan controller   faulty. Wire 1935 or 1936 between   MC59 and MC76 faulty. Temperature switch faulty. KNOWN INFO POSSIBLE PROBLEMS TEST OPTIONS REASON FOR QUESTION Voltage test. STE/ICE-R #89. If wire 1538 is loose, faulty, or shorted to ground, 22 to 28 vdc will not be input to fan controller from CB15. 8. Repair wire 1435 (see schematic Fig 2-67) or notify DS Maintenance. Verify repair, go to Step 19 of this Fault. YES NO Heater blower motor operates   indicating CB15 OK. Fan operates at low speed with   hydraulic selector switch in   AUTO or CRANE/SRW   position. Fan operates at low speed with   throttle position switch   depressed. Wire 1933 between MC59 and   MC128 OK. Wire 1932 between MC59 and   MC61 OK. Wire 1932 between MC61 and   MC128 OK. Temperature sensor OK. Wire 1538 OK. Wire 1435 from fan controller   faulty. Wire 1935 or 1936 between   MC59 and MC76 faulty. Temperature switch faulty. KNOWN INFO POSSIBLE PROBLEMS TEST OPTIONS REASON FOR QUESTION Continuity test. STE/ICE-R #91. If wire 1435 is loose or faulty, fan controller will not be grounded. Are 22 to 28 vdc measured on wire 1538 at connector MC73, terminal A? Is continuity measured on wire 1435 between connector MC73, terminal B and a known good ground?