Mercedes-Benz 2009 M-Class Operator's Manual page 192

Controls in detail
Climate control
i The air recirculation mode is activated
automatically at high outside
temperatures.
The indicator lamp in button
when the air recirculation mode is switched
on automatically.
A quantity of outside air is added after
approximately 30 minutes.
If you have turned off the air conditioning
or the outside temperature is below 41‡
(5†), the air recirculation mode will not
switch on automatically.
X
Deactivating: Press button :.
The indicator lamp in the button goes out.
i The manually selected air recirculation
mode is deactivated automatically:
after 5 minutes if the outside
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temperature is below approximately
41‡ (5†)
after 5 minutes if the air conditioning and
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air-drying are turned off
after 30 minutes if the outside
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temperature is above approximately
41‡ (5†)
190
Residual heat and ventilation
With the engine switched off, it is possible to
continue to heat or ventilate the interior for
is not lit
:
up to 30 minutes. This feature makes use of
the residual heat produced by the engine.
i How long the system will provide heating
depends on the coolant temperature and
the battery voltage.
Regardless of the temperature and air
volume set on the climate control panel, an
interior temperature is aimed at by 72‡
(22†) and the blower runs on low speed to
protect the vehicle battery.
X
Activating: Switch off the ignition.
X
Press button 9.
The indicator lamp in the button comes on.
X
Deactivating: Press button
The indicator lamp in the button goes out.
The residual heat is deactivated
automatically:
when the ignition is switched on
R
after approximately 30 minutes
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if the battery voltage drops
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if the coolant temperature is too low
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again.
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