The heating system provides heating, ventilation and defrosting for the windshield and side windows. The heater core is a heat exchanger supplied with coolant from the engine cooling system. Temperature is controlled by the temperature valve which moves an air door that directs air flow through the heater core for more heat or bypasses the heater core for less heat.
Vacuum actuators control the mode doors which direct air flow to the outlet ducts. The mode selector on the control panel directs engine vacuum to the actuators. The position of the mode doors determines whether air flows from the floor, panel, defrost or panel and defrost ducts (bi-level mode).