With the ignition switch in the RUN position, voltage is applied through the HVAC fuse (CKT 41) the Heater-A/C Control. Operation of the temperature control potentiometer causes the temperature control electric actuator to move the temperature air door to various positions. This allows heated air to mix with outside air to achieve the comfort level desired by the users. The control assembly provides a ground path through CKT 150 (BLK).

Control of air through the system is regulated by vacuum. At various points on the control, mode valves mix and direct cooled, heated and outside air through the air ducts. Refer to Vacuum System for additional information.