Interfaces The integrated automatic heating and air conditioning system has various interfaces available for the purpose of receiving and sending information on temperature control, compressor operation, rear window heater and the relevant fan stage. Body bus The following signals are transmitted from and to the instrument cluster via the Body bus: Speed signal Engine speed Coolant temperature Outside temperature Terminal 15 Terminal 61 Terminal 58g (locator lighting) Terminal 50 (starter) Compressor load moment Diagnosis CAN-bus The following signals are transmitted from and to the engine electronics via the CAN bus: Engine speed via CAN Request for air-conditioning compressor Temperature control Temperature control The required temperature in the passenger compartment (setpoint temperature ) is set by means of a rocker switch on the operating panel and shown in the display. The interior, heat exchanger, evaporator, outside and coolant temperatures are evaluated for the purpose of temperature control together with the driving speed and engine speed signals. Heater operation is based on the reheat principle. The air is cooled down by the evaporator and then heated up again to the required temperature by the heat exchanger. The temperature of the heat exchanger is controlled by a clocked water valve. In this way, the control unit calculates the valve opening times dependent on the above-specified input variables. The valve opening times are 0 ms at max. COLD and 3600 ms at max. WARM. A mechanical mixing air adjuster makes it possible to influence the outlet temperature at the ventilation nozzles. The temperature can be changed within the range from evaporator temperature to heat exchanger temperature.