Start with the easiest first. Check fuse #2.24 10amp in the fuse box inside the
vehicle. This provides power to the function selector switch (Off, Max, Normal, Vent, etc.). If fuse is good there are several other possibilities. I would remove the floor duct on the passenger side where the panel/floor door vacuum control motor is located. Ther are two vacuum lines going to it. Turn the selector switch from panel to floor with engine running and see if the motor pulls a vacuum on the two ports (with vacuum lines unplugged from motor). The vacuum should switch back and forth as you adjust the selector switch. If there is no vacuum on either one probe into the wires going to the vacuum motor with a voltmeter and see if it is getting voltage when the selector switch is moved back and forth. If it is getting voltage, the motor is bad. If it is not getting voltage you may have a wire or selector switch issue. Good Luck.