Ford 2004 Econoline Owner's Manual page 54

Climate Controls
Do not place objects on top of the instrument panel as these
objects may become projectiles in a collision or sudden stop.
REAR FAN SPEED ADJUSTMENT (IF EQUIPPED)
The rear fan controls adjust the
volume of air circulated in the rear
of the vehicle.
54
2004 Econoline (eco)
Owners Guide (post-2002-fmt)
USA English (fus)