Vacuum Hoses
WARNING: This page is about a different car, the 1995 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
An A/C plenum vacuum harness, which is attached to manual A/C control, directs vacuum to the different airflow doors within the heater air plenum chamber. Blower Control & A/C On-Off Switch
The rotary blower control switch on control assembly selects blower speed (LOW, MEDIUM LOW, MEDIUM HIGH and HIGH). With function control knob in OFF position, blower motor will not operate.