Air Volume Control
Fresh air enters the IHKA system through the fresh air inlets mounted in the bulkhead area behind the engine. The air passes through the micro/activated carbon filters positioned on each side of the engine compartment.
The left side is positioned above the brake power booster and the right side above the power distribution/E box.
The micro filters serve two functions, one is to filter out small dust and dirt particles. The second is to neutralize unpleasant odors. This function is carried out by the active carbon filter.
Care must be taken when servicing the micro filters or moving them for access to other components. When reinstalling the filters, ensure that the seals are properly installed to prevent odors from entering the interior.
The blower motor is controlled through an output stage that is mounted in a heat sink on the heater case.
The control lead from the IHKA module supplies a varying voltage (2.0 to 8.0 VDC) based on the position of the blower control rocker switch. The blower speed increases through the 15 steps until 8 volts is supplied to the control lead. At this point (the 16th step), the blower is running at maximum speed.
The speed of the blower fan is also influenced by the "Y" factor and degree of heating or cooling power requested.
When the IHKA system is switched ON, the blower fan will come ON at a speed that is dependent on the "Y" factor and system settings.
The battery charge condition also contributes to blower speed. When the battery drops below 12 volts, the blower speed signal to the blower output stage is reduced proportionately. Therefore a reduction in blower speed may be noticed.
To switch the system OFF, the rocker switch must be stepped down to the lowest setting and then toggled OFF.