Integrated heater control IHS

Integrated heater control IHS

This functional description covers the integrated heating control, IHS. The IHS can be used to adapt the in-vehicle climate to the individual needs of the passengers. Information is exchanged between the vehicle components involved via the body CAN data bus.

There are no differences for left-hand drive and right-hand drive vehicles. The control module with operating unit is always fitted in the same position in the vehicle.

The control module has the following functions (see also individual functional descriptions):

• Temperature control
  
• Air distribution
  
• Air flow control
  
• Recirculated-air mode
  
• Heated windscreen and rear window
  

Brief description of components

Control module/operating unit

The IHS control module records the signals of the IHS components and controls/regulates the heating process. The control module is at the same time the operating unit of the IHS.

The IHS control module also contains the bank of switches. The bank of switches can be used to operate the seat heating (if installed), the heated windscreen and heated rear window, as well as the electrical power windows. The centerlock button as well as the switches for the fog lamps and rear fog lamp are also built in.

Heater/air conditioner

The IHS heater/air conditioner is fitted underneath the instrument cluster in the centre, at the front bulkhead. The heater/air conditioner performs the tasks:

• Generation and regulation of air quantity
  
• Air distribution, air mixture (stratification)
  
• Transfer of heat output delivered by the cooling circuit
  

The heater/air conditioner is composed of the following components:

• Heat exchanger for heating system
  On the IHS, no heating system heat exchanger sensor is fitted.
  
• Flaps with drive and mechanical system
  The flap motors are connected directly to the IHS control module. Three flap motors are fitted in the IHS. The flaps serve to distribute the air and to mix hot and cold air.
  Fresh air recirculated-air flap: the amount of clean air drawn in by the blower is regulated with this flap.
  Air distribution flap: The air distribution flap mechanical system mechanically adjusts the air distribution flaps. The air distribution flap mechanical system is driven by the air distribution flap motor.
  The air distribution flap motor uses a Cam disk to set the air distribution. The air distribution flap motor has no detection of the actual position. In order to ensure unique positioning of the cam disk nonetheless, there are 2 cams of different widths on the cam disk. The micro-switch signals to the IHS control module that the cams have been passed over. This mechanism achieves reliable and rapid positioning of the cam disk.
  Temperature mixing flap: Subsequently, the temperature mixing flap guides the air-mass flow (depending on the set desired temperature value in the IHS controls fully or partially over the heat exchanger for the heating system and the electrical auxiliary heater (diesel engine).
  
• Blower with blower ballast resistor
  The blower creates the necessary air-mass flow. The blower is fitted after the fresh air recirculated-air flap in the heater/air conditioning system (pressing blower arrangement). The blower ballast resistor enables a manual 4-stage fan setting on the IHS controls.
  
• Electrical auxiliary heater
  The electrical auxiliary heater based on the PTC principle is fitted in the heater/air conditioner. The electrical auxiliary heater directly heats up the air to adjust the temperature of the vehicle interior. The electrical auxiliary heater is only fitted in diesel engines.
  

Microfilter

A microfilter with activated carbon is built into the IHS. 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.

Notes for Service department

Observe the following information for service:

General information

The following general data is provided for servicing the IHS:

Replacement of the electrical auxiliary heater

The electrical auxiliary heater can be replaced in service (the heater/air conditioner must be completely removed).

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 module (IHS)
  

Programming

Flash programming of IHS control module via the K-CAN is possible.

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