I just bought a 2001 Ford taurus. The heater works, but will only blow air through the defroster and floor outlets. It will not blow air through the vents on the dash panel.

Vacuum leak under the dashboard, probably at the automatic brake release.

Chances are You My Need A climate control Module, But You Need to Drop the Heater and AC Housing to make sure the Diverter doors are working,Since Fords Do have a Outside Leaf Catcher Problem It May just Be Leaves Preventing the Doors from Operating Properly,But then Again It requires that the Heater Box be dropped,Have Had some luck Using Compressed Air to Clean the debris into the A/C Drain but that will also have to be Blown Clear anyway Expect A few Hours of work to fix the Problem

Sounds like your hot/cold door is stuck on cold. Is the heat not hot either? If so that could be it. Perhaps your heater core. Good luck.

. Air won't blow out of the floor or center vents just defrost ? Do you have manual or automatic climate control ?
Air Flow Control
Air flow control is accomplished in the following manner:

• Primary control is through the function selector knob mounted on the A/C-heater function selector switch, which is part of the integrated control panel.
• The function selector knob has the following positions: OFF, MAX A/C, A/C, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST. The A/C-heater function selector switch combines a vacuum selector valve with an internal electrical switch.
• The vacuum selector valve directs source vacuum to various vacuum control motors (18A318). Refer to the Vacuum Control Diagram , System Airflow Schematics and Vacuum Control Chart .
• Two internal, single-pole electrical switches are also controlled by the A/C-heater function selector switch. The combination of these electrical switches controls the electrical supply to the A/C clutch and heater blower motor switch (18578).
• The position of the function selector knob determines the manner in which the system will operate.
• Each position of the function selector knob is detented for positive engagement.
• Vacuum Control Motors The vacuum control motors (18A318):
  
  • are located on the A/C evaporator housing, A/C recirculation air duct and heater air plenum chamber (18471).
  • direct system airflow to the vehicle interior as determined by the remote climate control module or manual override.
  • The five-passenger seating configuration has an additional vacuum control motor mounted on the heater air plenum chamber to control airflow to the rear seat A/C register (19893).
  
  

Are you saying the blower does not work, or you get no hot air ?

possibly the bled door is stuck open so only the cold air from a/c works when on defrost vs closing to allow heat to cycle through the system as defrost runs through the a/c system

There is no vacuum to the controls. Look for a vacuum hose that is no longer connected to the engine intake manifold and repair it.

you have a vacuum leak check vacuum lines

these are two diff systems working of the same control. Heater first, do you hear the fan running with the heater on all speeds, does any air come out of vents? Is it hot air? If you have air flow can you adjust it to defrost or floor?

heater is not blowinig warm air.