after much reading and searching online i was informed as to why my heater had defrost option only working...
i have a 2000 ranger with a 3.slow and found that one of the vacuum lines to the vacuum ball was either cut off or broke by the fire wall. i got a line connected to the ball and now all is well.......i was shocked. what ever happened to metal linkages?? lol
Reason for dumping metal linkage is because its easier to implement vacuum or electronic controlled vents. You don't have to route the linkage. (I'm talking about the solid rod linkage, I think cable would have been the best alternative). I guess vacuum and electronic systems came out to be a cheaper method.
As for ford going with vacuum: vacuum components are cheaper and IMO easier to diagnose than electronic components(personal opinion and will vary from person to person). It is 10x cheaper for a vacuum actuator than a electronic one.
Now why ford uses electronic blend door actuators beats me. I thought the cable style is fine. I guess maybe its easier to brake the blend door components with the manual style if you twist the know to fast/hard.
Quality Engineer (Electronics) for Kia Motors University of Tennessee Electrical Engineering Graduate 2000 XLT 2.5L A/T