Ford 1996 Aerostar Manual page 100

Driving uphill or on a steep grade
When the speed control is on, your vehicle may
significantly drop speed when driving uphill,
especially with a heavy load. If the speed drops
more than 8 to 14 mph (15 - 25 km/h) the
automatic speed control will, by design, be
canceled. You may have to temporarily resume
manual speed control while driving up a steep
grade in order to maintain the speed you desire.
If the speed control "dropped out" after your
climb is completed, the speed of your vehicle
can be reset with the SET ACCEL switch, or
returned to the previous set speed with the
RESUME switch, as long as you are driving over
30 mph (50 km/h).
To cancel speed control and then resume a set
speed:
119