1997 Ford Taurus front defrost not working

. 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).