Vacuum line problems (loss of vacuum) will make it blow only onto the windshield (defrost). Disconnected line or hole worn through vacuum line will do this. If so, it probably won't be going to the floor, only to the defrost.

95 Contour Zetec, ATX (wrecked, sitting in the barn) 95 Mystique Zetec, MTX 2000 Taurus SEL 3.0L Duratec 1994 Crown Victoria LX 4.6 V8 1993 Chevy Silverado 4.3 V6