My daughter's 2000 focus ZX3 has heat, but when we turn the selector to defrost, the heat continues to come out the dashboard vents. When the selector is turned to defrost, the AC light still comes on, so I think the selector switch is working.
Does the control knob feel right. It sounds like a door or flap isn't moving so as to divert the airflow to the defroster. I don't think these are vacuum operated- it has the old-fashioned bowden cables. So maybe one slipped off someplace.
so you flip it, the light come on but the air blowing out doesn't switch to the defrost vent. sounds like a cable prob or the cable ain't hooked up. move the selector the range of the dial and listen for the flap and get back to us