Ford 1997 Aerostar Manual page 71

Front control assembly with rear blower knob
In addition, an auxiliary unit fan switch is
located on the left side of the vehicle in line
with the second row of seats.
To control the auxiliary unit fan speed with this
switch, the rear fan switch on the front control
must first be set at the REAR CONT (control)
position.
Rear mounted auxiliary fan switch
68