Ford 1998 Crown Victoria Owner's Manual page 36

Controls and features
SPEED CONTROL (IF EQUIPPED)
To turn speed control on
Press ON.
Vehicle speed cannot be controlled
until the vehicle is traveling at or
above 48 km/h (30 mph).
Do not use the speed control in heavy traffic or on roads that
are winding, slippery, or unpaved.
Do not shift the gearshift lever into N (Neutral) with the speed
control on.
To turn speed control off
Press OFF or
Turn off the vehicle ignition.
Once speed control is switched off, the previously programmed set speed
will be erased.
36
ON
OFF
ON
OFF