Ford Windstar Owner's Manual page 116

This light does not indicate any problems with the speed control
system, but is a convenience to tell you when the speed control
system is actively maintaining a set speed.
Setting the Autolamp Delay System (If equipped)
By using the autolamp, you can set the headlamps to:
turn on the headlamps automatically at night
turn off the headlamps automatically during daylight
keep the headlamps on for up to three minutes after you
turn the key to OFF.
The autolamp system
Setting the autolamp
This feature allows the Autolamp circuit to be adjusted, to the
driver's liking, for the headlamps to turn on for the amount of
ambient light. If the driver desires the headlamps to come on
earlier when the sky is brighter or later when the sky is darker,
then the following procedure should be performed to satisfy the
driver's requirement.
Controls and Features
115