I have a 97 Ford Expedition, 2wd, Eddie Bauer Edition.
I'm having two problems with the heat & air:
1. Air will not blow out of floor vents, when I switch the knob to floor it blows out of the defrost vents only
2. As I turn the thermostat knob from cool to warm, output from vents (driver or defrost) reduces by about half, and the fan noise turns "deeper" inside the dash (if that makes sense) Turning the fan to high will get just less than half the air output on warm than on cool.

It should be noted that about four years ago the "air mixer" was replaced, because only hot air was coming out, not cool air. I cannot remember if the problem was present before then.
I also took apart the dash to replace dashboard lights in 2010, I know the foot vent problem was present then, not sure about the heater problem.
What can I do about this?

Thanks for the help.

. Perform diagnostics, if you have Electronic Air Temperature Control (EATC). Record any codes that were stored. Running the diagnostics will sometimes solve the problem. If you encounter a pending, rather than a hard fault code, terminate the diagnostics and erase all codes. This will often reset the blend door actuator.

. Replace the blend door actuator.

I think it's all vacuum.

It shouldn't be too hard to solve then.