Automatic Air Recirculation; Fresh Air Micro Filter System - BMW 1999-2005 M3 Service Manual

Heating and Air Conditioning
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Automatic air recirculation

As of model year 2000, automatic
recirculation control is available. This
system uses an air quality sensor (AUC)
(arrow), located at the top right corner of
the radiator, to detect high levels of air
pollution and automatically switch the
IHKA to recirculation of interior air. The
recirculation button on the IHKA control
panel can be toggled to allow automatic,
manual or no recirculation.
Once recirculation is turned on, it runs
until it is turned off using the button.
Once the ignition is turned off, the
recirculation setting is saved for 15
minutes, after which the IHKA system
reverts to fresh air mode. This feature
can be over-ridden using the Car
Memory feature, so that recirculating
interior air is automatically selected on
engine start-up.

Fresh air micro filter system

A fresh air micro filter system is used in
all E46 models. The filter is housed
below the fresh air inlet at the rear of the
engine compartment. The filter can be
serviced by releasing three-quick release
screws and removing a plastic cover.
Service
The heating system is part of the engine
cooling system and is sealed. The only
required service is periodic coolant
flushing. See 170 Radiator and
2/25/2009 11:16 PM