[sparkslg]

hey Mark cables are long gone for most Fords
you have a blend door motor (actuator) problem
this is very common , there are two gears inside the actuator and one of the two usually looses a few teeth thus causing the clicking or other noises when you turn the temp control knob
this part is under the dash and can be accessed by removing all floor ducting and vacuum actuator (center of dash floor area) It is about 3inches square and has 3 or 4 screws holding it to the plenum.It also has an electrical connector and is usually white in color.

hope this helps