Originally Posted by whippersnapper02
Its a bad fan motor resistor. Change it.
It is located directly below the blower motor itself. It helps to remove the blower to gain easy access, but it is possible to remove the resistor without removing the blower if you have small hands and patience.
The connector is prone to overheating and failure, so you may have to get one of those at Ford. I've read that AP stores are starting to stock resistors and connectors for Fords, but I haven't confirmed that.