Automatic Recirculated Air Control (AUC) IHKA RR

The basic function of the IHKA runs in the AUC mode. If the recirculated-air button (RECIRC) is pressed during the AUC mode, the recirculating air mode becomes active (LED lights up). Pressing the recirculated-air button once again takes you back to the AUC mode (LED off).

Recirculated-air mode

The RECIRCULATED AIR function can be used to prevent a deterioration in the air quality caused by external air impairment (e.g. waiting at traffic lights, driving through a tunnel, etc.) when the windows and sunroof are closed.

The RECIRCULATED AIR function is activated when

The fresh air flap is closed in max. one second. The recirculated air flap is opened in approx. four seconds.

The refrigerating circuit is not compulsorily cut in.

The RECIRCULATED AIR function is not saved before the control unit's sleep mode, that is, the function is cancelled after reset.

AUC mode

In the recirculated-air control (AUC) mode, automatic switches are made between fresh air and recirculated air mode depending on the quality of the ambient air.

A sensor system is used in the IHKA to measure the air quality. It sends a pulse-width-modulated signal to the control unit corresponding to the proportion of pollution. The control unit uses this to calculate an air quality level.

Start phase

When starting the vehicle, fresh air is always supplied for 60 seconds due to the AUC sensor heating-up time.

Forced ventilation with fresh air

A permanent request for recirculating air mode is interrupted by forced ventilation with fresh air mode. The reason for this is that the oxygen in the vehicle interior is used up in recirculating air mode. Moreover, in recirculating air mode, the relative humidity in the interior of the vehicle can increase due to the lack of fresh air. This results in condensation forming on the windows.

Function specification:

  1. Each valid recirculated-air function is activated for at least 30 seconds.
  2. At outside temperatures < 6°C, there are only reactions to signals indicating a medium air quality level. The maximum dwell time is 3 minutes, then fresh air is supplied for 1 minute.
  3. In the heating mode at outside temperatures ≥ 6°C, the recirculated air period is limited to 4 minutes, then fresh air is supplied for 1 minute.
  4. If the refrigerant compressor is also activated, at outside temperatures ≥ 6°C, the recirculated air period is limited to 12 minutes, then fresh air is supplied for 1 minute.
  5. At outside temperatures < 0°C, there are only reactions to signals indicating a poor air quality level. The maximum recirculated air period is 2 minutes, then fresh air is supplied for 1 minute.
  6. At speeds higher than 130 km/h, there are only reactions to signals indicating a medium air quality level.

Automatic recirculated air

This special function serves to cool the car interior rapidly. When extreme cooling capacity is required, in order to cool the car interior more quickly, the already cooler air inside the car is rerouted through the evaporator. This causes the temperature level to drop far more quickly than in normal operation.

The function runs initially for 12 minutes in full recirculated air mode and then always in partial recirculated air mode (fresh air 30% / recirculated air 100%). If the function is cancelled within the 12 minutes, the system will only switch into partial recirculated air mode the next time it is activated.

Automatic air recirculation is switched in the case of the following switching criteria: