engine MERCEDES-BENZ R320 2008 W251 Repair Manual

199 Controls in detail
Automatic transmission
Gear ranges
With the automatic transmission in drive
positionD, you can select a gear range for
the automatic transmission to operate
within.
You can limit the gear range by pressing
the left gearshift button on the steering
wheel gearshift control, and reverse the
gear range limit by pressing the right gear-
shift button on the steering wheel gearshift
control (
page 201).
The selected gear range appears in the
multifunction display.
1Current gear range
Effect
ïThe transmission shifts through
sixth gear only.
îThe transmission shifts through
fifth gear only.
éThe transmission shifts through
fourth gear only.
èThe transmission shifts through
third gear only.
With this selection you can use
the braking effect of the engine.
Effect
çThe transmission shifts through
second gear only.
Allows the use of engine’s
braking power when driving:

on steep downgrades

in mountainous regions

under extreme operating
conditions
æThe transmission operates in
first gear only.
For maximum use of engine’s
braking effect on very steep or
lengthy downgrades.

200 Controls in detail
Automatic transmission
Automatic shift program
The program mode selector switch is
located on the upper part of the center
console.
Program mode selector switch
C Comfort For comfort driving
S Sport For standard drivingThe selected program mode appears in the
multifunction display.
1Current program mode
Press program mode selector switch
repeatedly until the letter of the
desired program mode appears in the
multifunction display.
SelectCfor comfort driving:

The vehicle starts out in second
gear (both forward and reverse) for
gentler starts. This does not apply if
full throttle is applied or gear
range1 is selected.

Traction and driving stability are
improved on icy roads.

Upshifts occur earlier even when
you give more gas. The engine then
operates at lower rpms and the
wheels are less likely to spin.
SelectSfor standard driving:

The vehicle starts out in first gear.

Upshifts occur later.
!Never change the program mode when the
automatic transmission is out of park positionP.
This could result in a change of driving character-
istics for which you may not be prepared.
iThe last selected program mode (CorS) is
switched on when the engine is restarted.
iR 320 CDI 4MATIC only:
To help avoid overloading the torque converter,
the vehicle starts out in first gear, regardless of
the selected program mode.

201 Controls in detail
Automatic transmission
Steering wheel gearshift control
With drive positionD selected, you can
limit or extend the gear range.
1Left shift button: limiting gear range
2Right shift button: extending gear
rangeLimiting gear range
Briefly press left shift button1.
The transmission will shift to the next
lower gear as permitted by the shift
program. This action simultaneously
limits the gear range of the transmis-
sion (
page 199).
!Allow engine to warm up under low load use.
Do not place full load on the engine until the
operating temperature has been reached.
Shift into reverse gearR or park positionP only
when the vehicle is stopped.
Avoid spinning of a drive wheel for an extended
period when driving off on slippery road
surfaces. This may cause serious damage to the
drivetrain which is not covered by the
Mercedes-Benz Limited Warranty.
iYou cannot shift with the steering wheel
gearshift control buttons when the transmission
in positionP,N orR.
Warning!G
On slippery road surfaces, never downshift
in order to obtain braking action. This could
result in drive wheel slip and reduced
vehicle control. Your vehicle’s ABS will not
prevent this type of loss of control.
iTo avoid overrevving the engine when down-
shifting, the transmission will not shift to a lower
gear if the engine’s max. speed would be
exceeded.

202 Controls in detail
Automatic transmission
Extending gear range
Briefly press right shift button2.
The transmission will shift to the next
higher gear as permitted by the shift
program. This action simultaneously
extends the gear range of the transmis-
sion.Canceling gear range limitPress and hold right shift button2
until the cipher for the current gear
range disappears from the multifunc-
tion display (
page 199).
The transmission will shift from the
current gear range directly to gear
rangeD.
Shifting into optimal gear range
Press and hold left shift button1.
The transmission will automatically
select the gear range suited for optimal
acceleration and deceleration. This will
involve shifting down one or more
gears.Emergency operation (Limp-Home
Mode)
If vehicle acceleration becomes less re-
sponsive or sluggish or the transmission
no longer shifts, the transmission is most
likely operating in limp-home (emergency
operation) mode. In this mode only second
gear and reverse gear can be selected.
Stop the vehicle in a safe location.
Shift to park positionP.
Turn off the engine.
Wait at least 10 seconds before
restarting.
Restart the engine.
Shift to drive positionD (for second
gear) or reverse gearR.
Have the transmission checked at an
authorized Mercedes-Benz Light Truck
Center as soon as possible.
iIf you press on the accelerator when the en-
gine has reached its rpm limit, the transmission
will upshift beyond any gear range limit selected.

211 Controls in detail
Climate control
The climate control is operational when-
ever the engine is running. You can oper-
ate the climate control system in either the
automatic or manual mode. The system
cools or heats the interior depending on
the selected interior temperature and the
current outside temperature.Nearly all dust particles, pollutants and
odors are filtered out before outside air en-
ters the passenger compartment through
the air distribution system.
The air conditioning will not engage (no
cooling) if the A/C mode is deactivated
(
page 219).
Warning!G
When operating the climate control, the air
that enters the passenger compartment
through the air vents can be very hot or very
cold (depending on the set temperature).
This may cause burns or frostbite to unpro-
tected skin in the immediate area of the air
vents.
Always keep sufficient distance between un-
protected parts of the body and the air
vents. If necessary, use the air distribution
controls (
page 210) to direct the air to air
vents in the vehicle interior that are not in
the immediate area of unprotected skin.
Warning!G
Severe conditions (e.g. strong air pollution)
may require replacement of the filter before
its scheduled replacement interval.
A clogged filter will reduce the air volume to
the interior and the windows could fog up,
impairing visibility and endangering you and
others. Have a clogged filter replaced as
soon as possible at an authorized
Mercedes-Benz Light Truck Center.
Warning!G
Follow the recommended settings for heat-
ing and cooling given on the following pag-
es. Otherwise the windows could fog up,
impairing visibility and endangering you and
others.
iIf the vehicle interior is hot, ventilate the in-
terior before driving off, see “Summer opening
feature” (
page 244). The climate control will
then adjust the interior temperature to the set
value much faster.
Keep the air intake grille in front of the wind-
shield free of snow and debris.

212 Controls in detail
Climate control
Deactivating the climate control
system
Deactivating
Press button´ (page 210).
The indicator lamp on the button
comes on.Reactivating
Press buttonU (page 210).
Operating the climate control system
in automatic modeActivating
Press buttonU (page 210) while
the engine is running.
The indicator lamp on the button
comes on. The air volume and air distri-
bution are adjusted automatically.
Use temperature controls1 and7
(
page 210) to separately adjust the
air temperature on each side of the
passenger compartment.
The interior air temperature is adjusted
automatically.
Warning!G
When the climate control system is
switched off, the outside air supply and cir-
culation are also switched off. Only choose
this setting for a short time. Otherwise the
windows could fog up, impairing visibility
and endangering you and others.
iYou can also press button´
(
page 210) on the climate control panel.
If you press button| (
page 210) to reacti-
vate the climate control system, the defrosting
mode is activated.
iWhen operating the climate control system
in automatic mode, you will only rarely need to
adjust the temperature, air volume and air distri-
bution.
In automatic mode, cooling with dehumidify is
switched on. This function can be switched off if
necessary (
page 219).
iThe settings for the passenger side are also
used for the rear passenger compartment.

219 Controls in detail
Climate control
Air conditioning
The air conditioning is operational while
the engine is running and cools the interior
air to the temperature set by the operator.
In addition, the air conditioning dehumidi-
fies the interior air at outside temperatures
above 41°F (5° C) and helps prevent
window fogging.
Deactivating
It is possible to deactivate the air condi-
tioning (cooling) function of the climate
control system. The air in the vehicle will
then no longer be cooled or dehumidified.Press button9 (page 210).
The indicator lamp on the button goes
out.
Activating
Moist air can fog up the windows. You can
dehumidify the air with the air condition-
ing.
Press button9 (page 210) again.
The indicator lamp on the button
comes on.
The air conditioning uses the refrigerant
R134a. This refrigerant is free of CFCs
which are harmful to the ozone layer.
Residual heat and ventilation
With the engine switched off, it is possible
to continue to heat or ventilate the interior
for up to 30 minutes. This feature makes
use of the residual heat produced by the
engine.
Activating
Switch off the ignition (page 39).
Press button9 (page 210).
The indicator lamp on the button
comes on.
iCondensation may drip out from underneath
the vehicle. This is normal and not an indication
of a malfunction.
Warning!G
If you turn off the cooling function, the inte-
rior air is not dried. The windows can fog up
more quickly. Window fogging may impair
visibility and endanger you and others.
!If the air conditioning cannot be turned on
again, this indicates that the air conditioning is
losing refrigerant. The compressor has turned
off.
Have the air conditioning checked at the nearest
authorized Mercedes-Benz Light Truck Center.
iHow long the system will provide heating
depends on

the coolant temperature

the battery voltage
Regardless of the temperature and air volume
set on the climate control panel, an interior tem-
perature is aimed at by 72°F (22°C) and the
blower runs on low speed to protect the vehicle
battery.

225 Controls in detail
3-zone automatic climate control*
The automatic climate control is a 3-zone
intelligent automatic climate control
system. Your vehicle interior is divided
into 3 zones.With the help of a sun sensor, the
automatic climate control determines the
relation of the sun to the vehicle and auto-
matically adjusts the inside temperature
for each individual zone.The automatic climate control is oper-
ational whenever the engine is running. It
cools the vehicle’s interior according to the
angle and intensity of the sun’s rays, the
outside temperature and the selected tem-
perature. You can operate the automatic
climate control in either the automatic or
manual mode.
Nearly all dust particles, pollutants and
odors are filtered out before outside air
enters the passenger compartment
through the air distribution system.
Warning!G
When operating the automatic climate
control, the air that enters the passenger
compartment through the air vents can be
very hot or very cold (depending on the set
temperature). This may cause burns or frost-
bite to unprotected skin in the immediate
area of the air vents.
Always keep sufficient distance between
unprotected parts of the body and the air
vents. If necessary, use the air distribution
controls (
page 224) to direct the air to air
vents in the vehicle interior that are not in
the immediate area of unprotected skin.Warning!G
Severe conditions (e.g. strong air pollution)
may require replacement of the filter before
its scheduled replacement interval.
A clogged filter will reduce the air volume to
the interior and the windows could fog up,
impairing visibility and endangering you and
others. Have a clogged filter replaced as
soon as possible at an authorized
Mercedes-Benz Light Truck Center.

227 Controls in detail
3-zone automatic climate control*
Operating the automatic climate
control system in automatic mode
You can switch the automatic climate
control system on and off separately for
each zone as needed.
Activating
Press buttonU (page 224) while
the engine is running.
The indicator lamp on the button
comes on. Air volume and air distribu-
tion are controlled separately for each
zone.
Use temperature controls1 and9
(
page 224) to separately adjust the
air temperature on each side of the
passenger compartment.
The temperature of the interior is
adjusted automatically.
Deactivating
Press one button of the air distribution
(
page 224) or press button

orQ (
page 224).
The indicator lamp on the buttonU
goes out.
Depending on which button you press –
the air distribution button or the air vol-
ume button
or Q – automatic
control of either the air distribution or
air volume is switched off.
Setting the temperature
Use temperature controls1 and9
(
page 224) to separately adjust the air
temperature on each side of the passenger
compartment. You should raise or lower
the temperature setting in small incre-
ments, preferably starting at 72°F (22°C).
The automatic climate control will adjust
to the set temperature as fast as possible.
Increasing
Turn temperature control
1and/or9 slightly clockwise.
The automatic climate control system
will correspondingly adjust the interior
air temperature.
Decreasing
Turn temperature control
1and/or9 slightly counterclock-
wise.
The automatic climate control system
will correspondingly adjust the interior
air temperature.
iWhen operating the automatic climate con-
trol system in automatic mode, you will only
rarely need to adjust the temperature, air volume
and air distribution.
In automatic mode, cooling with dehumidify is
switched on. This function can be switched off if
necessary.

233 Controls in detail
3-zone automatic climate control*
Convenience opening:
Press button: for approximately
2 seconds.
The windows and/or tilt/sliding
sunroof will return to their previous
positions. You can release button:
once the opening procedure has
begun. The windows and tilt/sliding
sunroof continue opening until they
have reached their previous positions.
The indicator lamp on the button goes
out. The air recirculation mode is
deactivated.Vehicles with panorama roof*
Convenience closing:
Press and hold button: until the
windows and the tilt/sliding panel are
closed or have reached the desired po-
sition. The indicator lamp on the button
comes on. The air recirculation mode is
activated.
Convenience opening:
Press and hold button: until the
windows and the tilt/sliding panel are
opened or have reached the desired
position. The indicator lamp on the
button goes out. The air recirculation
mode is deactivated.
Air conditioning
The cooling function, only operational
when the engine is running, cools the
vehicle down to the selected interior
temperature. The cooling function also
dehumidifies the air in the vehicle interior,
thereby preventing the windows from
fogging up.
iCondensation may drip out from underneath
the vehicle. This is normal and not an indication
of a malfunction.
Warning!G
If you turn off the cooling function, the
interior air is not dried. The windows can fog
up more quickly. Window fogging may
impair visibility and endanger you and
others.