The heating system consists of an electric fan and a radiator (heating systems), located in the heater body, and pipes connecting the radiator to the engine cooling system. Hot coolant passing through the radiator heats the air in the heater. When using the temperature control panel, the heater flaps open, directing air from the heater into the vehicle's interior. When the fan is turned on, the air flow through the unit is regulated according to the position of the regulator. The fan speed is selected by turning the knob on the heater control panel on all recent models.
On earlier models, recirculation and air flow into the vehicle's interior were controlled by temperature control levers. By changing the position of the control lever, you can direct a stream of fresh or hot air through the internal nozzles or through the windshield heating nozzles (see Figure 9.2).
Figure 9.2. General view of heating and ventilation systems: A - cold or hot air; B - recirculation.
Later models use a rotary knob to control all heating and ventilation modes instead of the awkward sliding levers.