Rear temperature regulation

The temperature is regulated using an electronic unit working on the reheat principle. In air conditioner mode, the air drawn in is cooled to a constant temperature and then warmed up again to the temperature selected by the customer. The temperatuer can be selected independently for the left-hand and right-hand rear seat passengers. The electronic unit relies on two temperature sensors for its regulatory function, the interior temperature sensor and the evaporator temperature sensor. In addition, the ambient temperature and the coolant temperature are registered via the K-bus.

The following components are responsible for temperature regulation:

• An evaporator, which chills the air flowing in to a near constant temperature.
  
• A cut-off valve on each of the front and rear refrigerant circuits. The valves are OPEN when no current is flowing and CLOSED when placed under current.
  
• A water cut-off valve for the rear heat exchanger, which is controlled by the FHK via a relay. The valve is OPEN when no current is flowing and CLOSED when placed under current.
  
• A blower end stage.
  
• 4 mixing flaps, which independently control the blower temperature.
  

Ventilation flap motor:

• 0% means maximum cooling at the air vents
  
• 56% means maximum heating at the air vents (dependent on the stratification selected, the value can be as low as 46%)
  
• 100% means the ventilation flaps are closed
  

Footwell flap motor:

• 0% means the footwell flaps are closed
  
• 50% means maximum cooling
  
• 100% means maximum heating
  

The stratification setting is detected by the FHK by a stratification potentiomenter and influences the blower temperature at the air vents around the value selected. The air from the ventilation grille is then, for example, cooler than the air from the footwell vent.