Integrated automatic heating/air conditioning system (IHKA): Sensors

The following sensors are installed in the heating and air conditioning system:

• Interior temperature sensor 

  A force-ventilated interior temperature sensor with interior temperature sensor blower is fitted in the IHKA controls and in the automatic rear air conditioning system. The interior temperature sensor measures the air temperature drawn in from the passenger compartment by the integrated interior temperature sensor blower.

  As of 07/2012 the interior temperature sensor in the IHKA controls is no longer forced-ventilated. The force-ventilated interior temperature sensor is also discontinued in the automatic rear air-conditioning system.

• Refrigerant pressure sensor 

  The refrigerant pressure sensor is located in the pressure line between the capacitor and the evaporator. Depending on the sensor signal, the output of the air-conditioning compressor is reduced via the control unit of the integrated automatic heating/air-conditioning system (IHKA control unit) if the refrigerant pressure is too high. The junction box supplies the refrigerant pressure sensor with voltage. The data are evaluated in the junction box electronics (JBE). The prepared data is sent across the body CAN (K-CAN) to the IHKA control unit.

• Evaporator temperature sensor 

  The evaporator temperature sensor picks up the outlet temperature of the cooled air at the evaporator to prevent icing of the evaporator. The evaporator temperature sensor of the integrated automatic heating/air-conditioning system (IHKA) is directly connected to the IHKA control unit. The evaporator temperature sensor of the rear air conditioner is directly connected to the HKA control unit ("HKA" stands for "automatic rear air conditioning").

• Rain-light-solar-condensation sensor 

  The solar sensor and condensation sensor are parts of the rain-light-solar-condensation sensor. The solar sensor enables the integrated automatic heating and air conditioning system (IHKA) to take account of solar irradiation. The solar sensor measures the sunlight on the vehicle. The sunlight on the driver's side and front passenger side are detected separately. Sunlight compensation is only active in the automatic program.

  The condensation sensor enables the IHKA to detect window condensation at an early stage, even before the driver can detect it. Counter-measures (program for the prevention of condensation) can be taken in good time without the need for driver intervention. The condensation sensor provides the following information:

  • Temperature on inside of the windscreen
  • Air humidity on inside of the windscreen

  The sensor data is processed in the evaluation electronics unit of the rain-light-solar-condensation sensor. The rain-light-solar-condensation sensor provides the data via the LIN bus. The junction box electronics (JBE) adopts the signals into the corresponding CAN message and sends them. The IHKA control unit is bus user on the K-CAN. If the rain and/or condensation sensor system fails, a fault entry is made in the junction box electronics (JBE).

• Automatic air recirculation control sensor (AUC sensor) 

  The AUC sensor is a metal oxide sensor. This sensor is highly sensitive to various smells and pollutants that are typical of traffic.

  The AUC sensor is fitted on the microfilter compartment. The automatic air recirculation control sensor evaluates the concentration of carbon monoxide and nitrogen oxides in the intake fresh air. The automatic air recirculation control sensor converts the detected air quality (also referred as air grade) into an electrical signal. To simplify processing of the information, the air quality in divided into 10 stages:

  • Stages 0 to 10 (clean to severely contaminated)

  The AUC sensor sends the corresponding level as a digital signal on the LIN bus to the junction box electronics (JBE). The junction box electronics send the digital signal on the CAN bus to the IHKA control unit. If the automatic air recirculation control sensor has an emission level that is too high, then the integrated automatic heating/air conditioning system control unit (IHKA control unit) in the air recirculation function is automatically switched to (prerequisite: IHKA in the automatic mode).

• Heat exchanger sensor 

  Two sensors are installed in the integrated automatic heating/air-conditioning system (IHKA), as the blow-out temperature at the heat exchanger for the heating system is registered separately for the driver's and front passenger side. The sensors are directly connected to the IHKA control unit.

• Ventilation temperature sensor 

  Two sensors are installed in the integrated automatic heating/air-conditioning system (IHKA), as the blow-out temperature at the middle ventilation flap is registered separately for the driver's and front passenger side. In the rear air outlet in the center console, 1 sensor is installed (no left-right separation in the rear passenger compartment). The 3 sensors are connected to the IHKA control unit.

  The left-right separation means that 2 sensors are installed (on the right-hand and left-hand rear air outlet) in the rear air outlet in the center console IHKA High with rear automatic rear air-conditioning system (FKA). The sensors are connected to the FKA control unit. The FKA control unit evaluates the signals from the sensors. The signal is sent as a message on the CAN bus. The IHKA control unit uses this message to regulate the corresponding flap motor.

• Rear-cabin footwell-temperature sensor 

  The left-right separation means that 2 sensors are installed on the rear automatic rear air-conditioning system (FKA). One sensor is attached to each of the left and right footwell air outlets. The sensors are directly connected to the FKA control unit. The FKA control unit evaluates the signals from the sensors. The signal is sent as a message on the CAN bus. The IHKA control unit uses this message to regulate the corresponding rear footwell flap motor.

• Roof air vent temperature sensor 

  The two roof air vents are only installed in conjunction with the rear air conditioner. The left-right separation means that a roof air vent temperature sensor is installed in each roof air vent.

  The signals of the 2 sensors are picked up and digitized in the control panel of the rear air conditioner on the right. The control panel sends the signals on the LIN bus to the HKA control unit. The HKA control unit evaluates this information and activates the air distribution flap motors and mixing flap drives.