TM 10-3930-669-20 18.  HEATER BLOWER DOES NOT OPERATE IN HIGH (CONT). KNOWN INFO Heater operates in LOW. Heater blower switch OK. POSSIBLE PROBLEMS Lead wire 4 faulty. Fan blower motor faulty. KNOWN INFO Heater operates in LOW. Heater blower switch OK. Lead wire 4 OK. Fan blower motor OK. POSSIBLE PROBLEMS TEST OPTIONS Voltage test. STE/ICE-R #89. REASON FOR QUESTION If 22 to 24 vdc are not present, lead wire 4 is faulty.  If lead wire 4 is OK, fan blower motor is faulty. TEST OPTIONS Verify repair. REASON FOR QUESTION If heater blower operates, fault has been corrected. 2-226