The first thing to do is to remove the heater bower motor. it is just three tiny bolts in the engine compartment near the cab on the passanger side. Very often this will be filled with leaves and all sorts of other stuff that will restrict airflow. If you are only getting high speed for your blower then it is most likely the blower motor resistor. There are lots of posts on this problem as it seems to be very common so you can search for it for some good information. (Basicly its a pack of resistors) It is located close to the blower motor. It has a 6 sided plug with about 5 (?) wires goin into it. Its another easy thing to replace. i got one from a junkyard for 5 bucks. i dont know what ford charges. If you think its somewhere else in the circuit i can give you the testing procedure but you will need a multimeter or self powered test light. Hope this helps some.