Automatic recirculated air control, IHKA

Automatic recirculated air control, IHKA

This functional description covers the automatic recirculated air control (AUC) of the integrated automatic heating / climate control, IHKA. The AUC can assume 2 operating modes: recirculated air mode and AUC mode.

Brief description of components

Recirculated-air button

The AUC function is activated via the recirculated-air button. The operating mode is shown in the display. Pressing the recirculated-air button once activates the automatic recirculated-air control mode. Pressing the recirculated-air button again activates the recirculated air mode.

Sensor for automatic recirculated air control

The AUC sensor is fitted on the micro-filter compartment. The AUC sensor detects the following pollutant emissions:

• • Hydrocarbons (CH)
    
  • Carbon monoxide (CO)
    
  • Nitrogen oxides (nitrogen monoxide NO, nitrogen dioxide NO₂)
    

The junction box supplies the AUC sensor with voltage. The junction box electronics evaluate the data of the AUC sensor. This evaluated data is sent via the K-CAN to the IHKA control unit.

Microfilter

A microfilter with activated carbon is built into the IHKA. The activated carbon filter makes an additional contribution to cleaning the fresh air that enters of gaseous pollutant emissions. The state of the microfilter is not picked up.

System functions

Recirculated-air mode

In the recirculated air mode, in the event of a high pollutant load, e.g. in a traffic jam, the supply of fresh air can be blocked. The air in the vehicle interior is permanently recirculated. With recirculated air mode, the oxygen in the vehicle interior is used up. Furthermore, in the recirculated air mode the relative humidity in the vehicle interior can increase, which can lead to fogging over.

To ensure adequate fresh-air supply, the recirculated air mode has a time limit (30 min recirculated air mode -> 30 s partial fresh-air mode -> 30 min recirculated air mode -> etc.).

The recirculated air mode is activated as follows:

• the recirculated-air button on the operating unit is pressed
  
• AUC detects an ambient condition
  

The fresh air recirculated-air flap is closed. The refrigerant circuit is not force-activated. The recirculated air mode is saved before the idle state of the control unit is reached, i.e. the function is activated after a 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.

If the AUC sensor measures a rise in the pollutant emissions in the environment, the IHKA control unit automatically activates the recirculated air mode. To ensure adequate fresh-air supply, the recirculated air mode has a time limit:

• at outside temperatures below 0 °C:
  2 min recirculated air mode -> 1 min fresh-air mode -> 2 min recirculated air mode - > etc.
  
• at outside temperatures of 0 °C to 6 °C:
  3 min recirculated air mode -> 1 min fresh-air mode -> 3 min recirculated air mode - > etc.
  
• during operation without air-conditioning function at outside temperatures above 6 °C:
  4 min recirculated air mode -> 1 min fresh-air mode -> 4 min recirculated air mode - > etc.
  
• during operation with air-conditioning function at outside temperatures above 6 °C:
  12 min recirculated air mode -> 1 min fresh-air mode -> 12 min recirculated air mode - > etc.
  

When the AUC function is activated, during an engine start there is a switch for approx. 40 s to the fresh-air mode due to the warming phase of the AUC sensor.

Notes for Service department

Observe the following information for service:

Coding and programming

• Coding
  When coding the vehicle-specific data, the following details (among others) are taken into account:
  
  • Engine variant (diesel engine or petrol engine)
    
  • Version of the control unit (IHKA)
    
• Programming
  Flash programming of the IHKA control unit via the K-CAN is possible.
  

Country-specific versions

The temperature display can be switched to °C or °F using the on-board computer function.

No liability can be accepted for printing or other errors. Subject to changes of a technical nature