Ford Windstar Owner's Manual page 186

Inflated passenger-side air bag
The air bag will inflate only once. The system is
designed to function on a one-time-only basis. If the air
bag is inflated, THE AIR BAG WILL NOT FUNCTION
AGAIN AND MUST BE REPLACED IMMEDIATELY. If
the air bag is not replaced, this will increase the risk of
injury in a subsequent collision.
To ensure that the air bag system will operate as intended in a
crash, the system is equipped with a diagnostic module, which
controls a readiness lamp and a warning tone. The diagnostic
module monitors its own circuits, the air bag electrical system,
the air bag readiness light, the air bag power and the air bag
inflators.
Seating and Safety Restraints
WARNING
185