no heater on a '97 Taurus on 1997 Ford Taurus

The heater will only blow cold air, so it actually isn't a heater at all. I'm wondering if the air blend damper actuator may be the problem. When the temp selector knob is turned from cold to hot, or hot to cold, I hear what I think is the sound of the blend damper moving as it should. Do I need to visually confirm its operation? There is good flow through the heater core. Could it be air locked? Is there a piece of the puzzle that I'm missing? Thanks.

Asked by for the 1997 Ford Taurus
How hot do your upper and lower radiator hoses get when the car is fully warmed up? what does your temp gauge say? In other words, make sure that the thermostat is not stuck open.