Automatic Climate Control - BMW 3-series convertible Complete Vehicle Workbook

Automatic Climate Control

The E93 Convertible is available with the IHKA system as standard
equipment. This IHKA system functions much the same way as
the E92. However, some additional functions have been added to
enhance AC operation in the convertible environment.
Due to the RHT, the E93 functions as two vehicles in one - a
coupe and an open top convertible. In the past, using the AC with
the top down creates a less than optimal situation for the driver.
When the top is down, outside temperature variations and changes
in solar radiation can now influence the IHKA system with less than
accurate information. Also, the "ram air pressure compensation"
feature in BMW IHKA systems is not desirable when the top is
down.
This situation forces the driver to continually adjust the temperature
and blower controls for maximum comfort. So, a "convertible top
mode" has been introduced into the E93.
This mode is activated when the top is down. A signal from the
convertible top module to the IHKA provides the activation for the
convertible top mode.
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E93 Complete Vehicle Workbook
This mode requires no additional components or sensors. Only
the "top down" signal from the CTM is required.
On vehicles with CCC (CID), the convertible top mode can be
selected and disabled. On vehicles without CCC, the convertible
top mode is always active when the top is down.
The parameters for controlling the ventilation are based on the
sun's intensity, driving speed and outside temperature. This
program ensures optimum heating/ventilation comfort for the
occupants.