TM 10-3930-669-20 2-13.  ENGINE SYSTEM TROUBLESHOOTING (CONT). 10.  HEATER DOES NOT BLOW WARM OR HOT AIR. INITIAL SETUP Tools and Special Tools Equipment Condition Tool Kit, General Mechanic's: Automotive Engine OFF (TM 10-3930-669-10) (Item 1, Appendix B) Engine oil level full (TM 10-3920-669-10) MAIN POWER switch OFF (TM 10-3930-669-10) Parking brake applied (TM 10-3930-669-10) Wheels chocked (TM 10-3930-669-10) References TM 10-3930-669-10 KNOWN INFO Cool air passes from heater duct. POSSIBLE PROBLEMS Heater temperature control faulty. Heater cable faulty. Heater valve faulty. Engine oil cooler thermostat faulty. TEST OPTIONS Visual inspection. REASON FOR QUESTION If temperature control is faulty, air temperature will not adjust. 2-116