TM 10-3930-669-20 10.  HEATER DOES NOT BLOW WARM OR HOT AIR (CONT). KNOWN INFO Cool air passes from heater duct. Heater temperature control OK. Heater cable OK. Heater valve OK. POSSIBLE PROBLEMS Engine oil cooler thermostat faulty. KNOWN INFO Cool air passes from heater duct. Heater temperature control OK. Heater cable OK. Heater valve OK. Engine oil cooler thermostat OK. POSSIBLE PROBLEMS TEST OPTIONS Operation test. REASON FOR QUESTION If engine oil cooler thermostat is faulty, air temperature will not adjust. TEST OPTIONS Verify repair. REASON FOR QUESTION If heater blower moves hot air, fault has been corrected. 2-120