Why is my heater blowing cool air?

Make SURE cooling system is FULL.... Crank engine and let run until fully warm with heater on ... Feel of both heater hoses under hood ... Both should be HOT enough that you have to let go!.. If only one hose is that hot... Try flushing out heater core... I do this @ the shop with a rig I made up using water and compressed air... Search YouTube for a how to vid or get some hands-on help from a car savvy buddy... IF BOTH hoses are hot.. Suspect temperature control door//baffle inside heater case isn't functioning correctly and may that be an actuator issue..... You dig?