2002 Ford Escort air in car wont switch from defrost to any

The blend air door determines if you get AC or heat. If the air flow is only through the defroster, you are dealing with a vacuum leak (most likely under the dash). The vents that guide air flow in different directions are actuated by vacuum. If there is a leak, it goes to a default, the defroster. Check for cracked, disconnected, or loosed hoses under the dash and let me know what you find.

Joe