Cold Air from Heater

hmm i used to have the same problem with my car, i would have to be driving for over 15min for it to stay hot. Heating your car is pretty simple basically when you run your engine the water pump in the car pushes antifreeze all throughout your engine to cool it down. So you have antifreeze constantly being flushed through your engine and you also have antifreeze in you radiator. The radiator is used to cool the fluid. The fluid goin through the engine is hot. So when the antifreeze is going on its route it passes through what is known as a heater core which is usually located at the rear of the engine under the passenger side dash. the fluid heats up the heater core which is made of metal. To get heat into your car there is a fan blower that blows air through that heater core and into the cabin of the car. the only other thing i could think of is maybe the heater core is partially clogged.

I would agree with billy. you could have a plugged heater core. you could also could have a problem with a mood door inside the dash. Inside most hvac units there are doors that control the were the air flows. the one that controls the temp. could be opening and closing when it is not suppose to and would cause you temp to change.

Keep in mind as well, that Ford makes use of a heater control valve under the hood that regulates the flow of coolant into the heater core from the radiator. Has the same basic concept as an EGR valve and if it went faulty, would give you the symptoms you are experiencing.