Heat Control Switch

I have a 1999 Ford F-150. While adjusting the temp control it started to feel like something was slipping and catching. If I turn it from hot to cold a couple of times, it will catch and work fine. I replaced the electric switch behind the knob in the dash. Did not help. Now if I turn it from hot to cold nothing happens and it feels like something has let loose. I'm assuming the flapper cable has come loose. Can I get to this under the hood or under the dash?
Can someone help me with some guidance? Thanks in advance. Mark.

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

Thanks for the quick reply sparkslg. I replaced the blend door motor, still does not work. I took the old one apart and the gears were fine. Now, I removed the blend door motor from the heater and turn the temp control and nothing moves. Also the new switch I replaced behind the temp control does not feel right. It does not turn smoothly. What's the chance I got a bad one? Everything else related to the heater works and I doubt this item has it's own fuse. I do have a multimeter so if I knew which terminals to check I could see if its a wiring problem. Thanks again in advance. Mark.