It looks like we have to guess at what kind of Ford you are driving and can't give you any specifics to your car but they all work the same way.
The temperature is controlled by the use of an air mix door that is operated by an electric motor/actuator. This door can be jammed or the actuator can be inoperative or have stripped plastic gears internally.
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Wednesday, April 20th, 2011 AT 12:30 PM