Function Selector Switch Vacuum Application Chart
WARNING: This page is about a different car, the 2003 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
A leak in the vacuum control circuits will send all airflow to the defroster outlets. This condition may occur during acceleration indicating a slow leak, exist at all times indicating a large leak, or it may exist only when specific functions are selected indicating a leak in that portion of the circuit.