Ford 1999 Windstar Owner's Manual page 205

Maintenance and care
3. Remove the cabin air filter access
cover.
4. Lift and remove the cabin air
filter.
5. Slide the new filter into the filter opening, ensuring proper orientation
of the filter. The black rubber seal around the filter perimeter should be
closer to the bottom of the opening when installed.
6. With your fingertips, ensure that the filter is pushed down properly.
The filter is seated when it fits snugly into the filter housing.
7. Reinstall the access cover.
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