Check the thermostat on your engine if good then "flush" the Heater core (its like an small radiator Inside of your car) the "hot" water circulates inside of the heater core and the blower "blows air through it" and Heats the air but when the water its not hot the blower just passes cold air.
The Heater control usually its a "valve" that allows the Hot water from the engine to go to the heater core and the air get warm.
Check the heater core. Could be "Plug" also check the valve that allows the engine hot water to enter the heater core.
Wednesday, November 28th, 2007 AT 12:20 PM