key battery MERCEDES-BENZ R-Class 2012 W251 Owner's Guide

Useful information
i This Operator's Manual describes all
models and all standard and optional
equipment of your vehicle available at the
time of publication of the Operator's
Manual. Country-specific differences are
possible. Please note that your vehicle may
not be equipped with all features
described. This also applies to safety-
related systems and functions.
i Please read the information on qualified
specialist workshops ( Y page 24).
Exterior lighting
Important safety notes
For reasons of safety, Mercedes-Benz
recommends that you drive with the lights
switched on even during the daytime. In some
countries, operation of the headlamps varies
due to legal requirements and self-imposed
obligations.
Information about driving abroad
Converting to symmetrical low beam
when driving abroad: switch the headlamps
to symmetrical low beam in countries in
which traffic drives on the opposite side of the
road to the country where the vehicle is
registered. This prevents glare to oncoming
traffic. Symmetrical lights do not illuminate
as large an area of the edge of the road.
Have the headlamps converted at a qualified
specialist workshop, e.g. an authorized
Mercedes-Benz Center, as close to the border
as possible before driving in these countries.
Converting to asymmetrical low beam
after returning: have the headlamps
converted back to asymmetrical low beam at
a qualified specialist workshop, e.g. an
authorized Mercedes-Benz Center, as soon as
possible after crossing the border again.
Light switch
Operation1 WLeft-hand standing lamps2XRight-hand standing lamps3$Lights off/daytime running lamps4ÃAutomatic headlamp mode/daytime
running lamps5 TParking lamps, license plate and
instrument cluster lighting6 LLow-beam/high-beam headlamps7RVehicles without front fog lamps:
rear fog lamp7 NVehicles with front fog lamps: front
fog lamp8 RVehicles with front fog lamps: rear
fog lamp
The turn signals, high-beam headlamps and
the high-beam flasher are operated using the
combination switch ( Y page 117).
! Switch off the parking lamps and standing
lamps when you leave the vehicle. This
prevents the battery from discharging.
The exterior lighting (except the parking/
standing lamps) switches off automatically if
you:
R remove the SmartKey from the ignition lock
R open the driver's door with the SmartKey
in position 0
If you hear a warning tone when you leave the
vehicle, the lights may still be switched on.
114Exterior lightingLights and windshield wipers

Rear overhead control panel (second row of seats)
:Switches the reading lamp on/off
Rear overhead control panel (third row of seats)
:p Switches the left-hand reading lamp
on/off;p Switches the right-hand reading
lamp on/off
Interior lighting control
Important notes
In order to prevent the vehicle's battery from
discharging, the interior lighting functions are
automatically deactivated after some time
except for when the SmartKey is in position
2 in the ignition lock.
Automatic interior lighting control
XTo switch on/off: press the | button.
When the automatic interior lighting
control is activated, the button is flush with
the overhead control panel.The interior lighting automatically switches
on if you:
R unlock the vehicle
R open a door
R remove the SmartKey from the ignition lock
The interior light is activated for a short while
when the SmartKey is removed from the
ignition lock. You can activate this delayed
switch-off using the on-board computer
( Y page 208).
Manual interior lighting controlXTo switch the front interior lighting on/
off: press the c button.XTo switch the rear interior lighting on/
off: press the v button.XTo switch the reading lamps on/off:
press the p button.
Crash-responsive emergency lighting
The interior lighting is activated automatically
if the vehicle is involved in an accident.
XTo switch off the crash-responsive
emergency lighting: press the hazard
warning lamp button.
or
XLock and then unlock the vehicle using the
key.
Replacing bulbs
Important safety notes
Xenon bulbs
If your vehicle is equipped with Xenon bulbs,
you can recognize this by the following: the
cone of light from the Xenon bulbs moves
from the top to the bottom and back again
when you start the engine. For this to be
observed, the lights must be switched on
before starting the engine.
Replacing bulbs119Lights and windshield wipersZ

The climate control system switches to the
following functions:
R cooling with air dehumidification on
R high airflow 19
R high temperature 19
R air distribution to the windshield and
front side windows
R air-recirculation mode offXTo switch off: press the ¦ button.
The indicator lamp in the ¦ button goes
out. The previously selected settings come
into effect again. The cooling with air
dehumidification function remains on. Air-
recirculation mode remains deactivated.
or
XPress the ^ button.
or
XPress the à button.
or
XTurn the temperature control clockwise or
counter-clockwise.
or
XPress the K or I button.
Defrosting the windows
Windows fogged up on the inside
XActivate the cooling with air
dehumidification function Á.XActivate automatic mode Ã.XIf the windows continue to fog up, activate
the defrosting function ( Y page 138).
i
You should only select this setting until
the windshield is clear again.
Windows fogged up on the outsideXSwitch on the windshield wipers.XPress the P/\ 20
or O /c 20
air distribution button.
i You should only select this setting until
the windshield is clear again.
Rear window defroster
Activating/deactivating
GWARNING
Any accumulation of snow and ice should be
removed from the rear window before driving.
Visibility could otherwise be impaired,
endangering you and others.
The rear window defroster has a high current
draw. You should therefore switch it off as
soon as the window is clear as it only switches
off automatically after several minutes.
If the battery voltage is too low, the rear
window defroster may switch off.
XTurn the SmartKey to position 2 in the
ignition lock.XPress the ª button.
The indicator lamp in the ª button lights
up or goes out.
Problems with the rear window
defroster
If the indicator lamp in the ª rear window
defroster button flashes, the on-board
voltage is too low or the roof is open. The rear
window defroster has deactivated itself
prematurely or cannot be activated.
XSwitch off any consumers that are not
required, e.g. reading lamps or interior
lighting.
When the battery is sufficiently charged,
the rear window defroster is activated
again automatically.19 Depending on the outside temperature.
20 Canada only.Operating the climate control system139Climate controlZ

Problems with the engineProblemPossible causes/consequences and M SolutionsThe engine does not
start. The starter motor
can be heard.R There is a malfunction in the engine electronics.
R There is a malfunction in the fuel supply.XBefore attempting to start the engine again, turn the SmartKey
in the ignition back to position 0 or press the Start/Stop button
repeatedly until all indicator lamps in the instrument cluster go
out.XTry to start the engine again ( Y page 146). Avoid excessively
long and frequent attempts to start the engine as these will drain
the battery.
If the engine does not start after several attempts:
XConsult a qualified specialist workshop, e.g. an authorized
Mercedes-Benz Center.The engine does not
start. You cannot hear
the starter motor.The on-board voltage is too low because the battery is too weak
or discharged.XJump-start the vehicle ( Y page 313).
If the engine does not start despite attempts to jump-start it:
XConsult a qualified specialist workshop, e.g. an authorized
Mercedes-Benz Center.The starter motor was exposed to a thermal load that was too high.XAllow the starter motor to cool down for approximately two
minutes.XTry to start the engine again.
If the engine still does not start:
XConsult a qualified specialist workshop, e.g. an authorized
Mercedes-Benz Center.Driving149Driving and parkingZ

Problems with fuel and the fuel tankProblemPossible causes/consequences and M SolutionsFuel is leaking from the
vehicle.GRisk of explosion or fire
The fuel line or the fuel tank is defective.
XTurn the SmartKey to position 0(Y page 145) in the ignition lock
immediately and remove it.XDo not restart the engine under any circumstances.XConsult a qualified specialist workshop.The fuel filler flap
cannot be opened.The fuel filler flap is not unlocked.
or
The SmartKey battery is discharged.XUnlock the vehicle using the mechanical key ( Y page 75).XOpen the tailgate.XManually unlock the fuel filler flap using the emergency release
( Y page 158).The fuel filler flap is unlocked, but the opening mechanism is
jammed.XManually unlock the fuel filler flap using the emergency release
( Y page 158).XConsult a qualified specialist workshop.The engine will not
start.The fuel tank of a vehicle with a diesel engine has been run
completely dry.XRefuel the vehicle with at least 5.3 US qt (5 liters) of diesel.XTurn the ignition on for at least 10 seconds ( Y page 145).XStart the engine continuously for up to 10 seconds until it runs
smoothly.
If the engine does not start:
XTurn the ignition on again for approximately 10 seconds
( Y page 145).XStart the engine again continuously for up to 10 seconds until
it runs smoothly.
If the engine does not start after three attempts:
XConsult a qualified specialist workshop.160RefuelingDriving and parking

automatic transmission shifts to P
automatically.
Using KEYLESS-GOXPress the Start/Stop button (Y page 145).
The engine stops and all the indicator
lamps in the instrument cluster go out.
i When the driver's door is closed, this
corresponds to SmartKey position 1. When
the driver's door is open, it corresponds to
SmartKey position 0 or "SmartKey
removed".
i If you use the Start/Stop button to switch
off the engine, the automatic transmission
shifts to N automatically. If you then open
the driver's or front-passenger door, the
automatic transmission shifts to P.
i In an emergency, the engine can be
turned off while the vehicle is in motion by
pressing and holding the Start/Stop button
for three seconds.
Parking brake
GWARNING
Engaging the parking brake while the vehicle
is in motion can cause the rear wheels to lock
up. You could lose control of the vehicle and
cause an accident. In addition, the vehicle's
brake lights do not light up when the parking
brake is engaged.
GWARNING
When leaving the vehicle, always remove the
SmartKey from the starter switch, take it with
you, and lock the vehicle. Do not leave
children unattended in the vehicle, or with
access to an unlocked vehicle. Children could
release the parking brake and/or shift the
automatic transmission out of park position
P , either of which could result in an accident
and/or serious personal injury.
XTo apply: depress parking brake ; firmly.
When the engine is running, the $ (USA
only) or J (Canada only) indicator lamp
lights up in the instrument cluster.XTo release: depress the brake pedal and
keep it depressed.XPull release handle :.
When the ignition is switched on or the
engine is running, the $ (USA only) or
J (Canada only) indicator lamp goes out
in the instrument cluster.
Parking the vehicle for a long period
If you leave the vehicle parked for longer than
four weeks, the battery may be damaged by
exhaustive discharge.
XConnect a trickle charger.
i You can obtain information about trickle
chargers from a qualified specialist
workshop, e.g. an authorized Mercedes-
Benz Center.
If you leave the vehicle parked for longer than
six weeks, the vehicle may suffer damage as
a result of lack of use.
XVisit a qualified specialist workshop and
seek advice.164ParkingDriving and parking

If children open a door, they could injure other
persons or get out of the vehicle and injure
themselves or be injured by following traffic.
Do not expose the child restraint system to
direct sunlight. The child restraint system's
metal parts, for example, could become very
hot, and the child could be burned on these
parts.GWARNING
Never touch the heating element or sides of
the lighter; they are extremely hot. Hold the
knob only.
Make sure any children traveling with you do
not injure themselves or start a fire with the
hot cigarette lighter.
! The 12 V socket in the cigarette lighter
can be used for accessories (up to a
maximum of 85 W) as long as they have the
standard socket type for cigarette lighters.
Note that the socket in the cigarette lighter
can be damaged when connecting
accessories, for example by frequent
insertion and removal or by sockets that do
not fit correctly. A damaged socket can
cause the cigarette lighter to stop working.
! The cigarette lighter in the center console
in the front compartment is not intended
for operating the tire inflation compressor.
XTurn the SmartKey to position 2 in the
ignition lock.XTo open: open cover : (Y page 249).XPress in cigarette lighter ;.
Cigarette lighter ; will pop out
automatically when the heating element is
red-hot.
12 V sockets
Points to observe before use
! The socket in the center console and the
socket in the cargo compartment are not
intended for operating the tire inflation
compressor.
The sockets can be used for accessories, e.
g. lamps or mobile phone chargers with a
maximum current draw of 240 W (20 A).
If you use the sockets for long periods when
the engine is switched off, the battery may
discharge.
XTurn the SmartKey to position 2 in the
ignition lock.
i You can also use the power sockets when
the SmartKey is in position 1 in the ignition
lock.
An emergency cut-out ensures that the on-
board voltage does not drop too low. If the
on-board voltage is too low, the power to
the sockets is automatically cut. This
ensures that there is sufficient power to
start the engine.
Features267Stowing and featuresZ

XMake sure the vehicle is stationary and the
ignition is switched off.XTurn the SmartKey to position
2 (Y page 145) in the ignition lock.
Use the SmartKey instead of the Start/
Stop button on vehicles with KEYLESS-GO.XDepress and hold the brake pedal.XShift the automatic transmission to
position N.XRelease the brake pedal.XRelease the parking brake.XSwitch off the ignition and leave the
SmartKey in the ignition lock.
! Make sure that:
R the side windows and the sliding sunroof
are fully closed.
R the ventilation/heating is switched off
(the OFF button has been pressed).
R the windshield wiper switch is in position
0 .
Otherwise, the vehicle might be damaged.
After using an automatic car wash, wipe off
wax from the windshield and the wiper
blades. This will prevent smears and reduce
wiping noises caused by residue on the
windshield.
Washing by hand
Carefully remove all deposits of road salt as
soon as possible when driving in winter.
Also, clean the insides of the wheels when
washing the underbody of the vehicle.
XDo not use hot water and do not wash the
vehicle in direct sunlight.XUse a soft car sponge for cleaning.XUse a gentle cleaning agent, e.g. a
Mercedes-Benz approved car shampoo.XWash down the vehicle with a gentle water
jet.XDo not point the water jet directly at the air
inlets.XUse plenty of water and rinse the sponge
frequently.XRinse the vehicle with clean water and dry
it thoroughly with a chamois.XDo not allow the cleaning agent to dry on
the paintwork.
Power washers
GWARNING
Do not use power washers with circular-jet
nozzles (dirt grinders) to clean your vehicle, in
particular the tires. You could otherwise
damage the tires and cause an accident.
! Always maintain a distance of at least
11.8 in (30 cm) between the vehicle and the
power washer nozzle. Information about
the correct distance is available from the
equipment manufacturer.
Move the power washer nozzle around
when cleaning your vehicle.
Do not aim directly at any of the following:
R tires
R door gaps, roof gaps, joints etc.
R electrical components
R battery
R connectors
R lights
R seals
R trim elements
R ventilation slots
Damaged seals or electrical components
can lead to leaks or failures.
Cleaning the wheels
! Do not use acidic wheel cleaning products
to remove brake dust. This could damage
wheel bolts and brake components.
! Do not park the vehicle for an extended
period straight after cleaning it, particularly
after having cleaned the wheels with wheel
cleaner. Wheel cleaners could cause
increased corrosion of the brake discs and
brake pads/linings. For this reason, you
should drive for a few minutes after
Care289Maintenance and careZ

Wear suitable protective
clothing, in particular
gloves, an apron and a face
mask.
Immediately rinse acid
splashes off with clean
water. Consult a doctor if
necessary.Wear eye protection.Keep children away.Observe this Operator's
Manual.HEnvironmental noteBatteries contain dangerous
substances. It is against the
law to dispose of them with
the household rubbish. They
must be collected separately
and recycled to protect the
environment.Dispose of batteries in an
environmentally friendly
manner. Return discharged
batteries to a qualified
specialist workshop, e.g. an
authorized Mercedes-Benz
Center, or to a special
collection point for old
batteries.GWARNING
Failure to follow these instructions can result
in severe injury or death.
Never lean over batteries while connecting.
You might get injured.
Battery fluid contains sulfuric acid. Do not
allow this fluid to come in contact with eyes,
skin or clothing. In case it does, immediately
flush affected area with water and seek
medical help if necessary.
A battery will also produce hydrogen gas,
which is flammable and explosive. Keep
flames or sparks away from battery, avoid
improper connection of jumper cables,
smoking etc.GWARNING
Do not place any metal objects on the battery
as this could result in a short circuit.
Use leak-proof batteries only to avoid the risk
of acid burns in the event of an accident.
Take care that you do not become statically
charged, e.g. by wearing synthetic clothing or
rubbing against textiles. For this reason, you
also should not pull or push the battery over
carpets or other synthetic materials.
Never touch the battery first. First, touch the
outside body of the vehicle in order to release
any possible electrostatic charges.
Do not rub the battery with rags or cloths. The
battery could explode if touched due to
electrostatic charge or due to spark
formation.
! Before working on the battery, e.g.
loosening the battery terminals, switch off
the engine and remove the SmartKey from
the ignition. On vehicles with KEYLESS-GO,
make sure that the ignition is switched off.
Check that all the indicator lamps in the
instrument cluster are off. You may
otherwise destroy electronic components,
such as the alternator.
! Like other batteries, the vehicle battery
may discharge over time if you do not use
the vehicle. In this case have the battery
checked at a qualified specialist workshop,
such as an authorized Mercedes-Benz
Center. You can also charge the battery
with a charger recommended by Mercedes-
Benz. Contact an authorized Mercedes-
Benz Center for more information.
Battery311Breakdown assistanceZ

The battery and the cover of the positive
terminal clamp must be installed securely
during operation.
i Remove the SmartKey if you park the
vehicle and do not require any electrical
consumers. The vehicle will then use very
little energy, thus conserving battery
power.
Mercedes-Benz recommends that you do not
carry out work on batteries yourself, e.g.
removing or charging. Always have this work
performed at a qualified specialist workshop,
e.g. an authorized Mercedes-Benz Center.
i If the power supply has been interrupted,
e.g. if the battery has been reconnected,
you must carry out the following tasks:
R set the clock ( Y page 206).
On vehicles with COMAND and a
navigation system, the clock is set
automatically.
R reset the sliding sunroof ( Y page 90).
R reset the panorama roof with power tilt/
sliding panel ( Y page 92).
R reset the function for automatically
folding the exterior mirrors in/out by
folding the mirrors out once
( Y page 110).
R reset the side windows ( Y page 89).
Charging the battery
GWARNING
Never charge a battery still installed in the
vehicle unless a battery charger unit approved
by Mercedes-Benz is being used. Gases may
escape during charging and cause explosions
that may result in paint damage, corrosion or
personal injury.
A battery charger unit specially adapted for
Mercedes-Benz vehicles and tested and
approved by Mercedes-Benz is available as an
accessory. It permits the charging of the
battery in its installed position. Contact an
authorized Mercedes-Benz Center for further
information and availability.
Charge the battery in accordance with the
separate instructions for the battery charger.GWARNING
There is a risk of acid burns during the
charging process due to the gases which
escape from the battery. Do not lean over the
battery during the charging process.
GWARNING
Battery acid is caustic. Avoid contact with the
skin, eyes or clothing.
! Only charge the installed battery with a
battery charger which has been tested and
approved by Mercedes-Benz. These battery
chargers allow the battery to be charged
while still installed.
! Only use battery chargers with a
maximum charging voltage of 14.8 V.
! Only charge the battery using the jump-
starting connection point.
The jump-starting connection point is in the
engine compartment ( Y page 313).
XOpen the hood ( Y page 282).XConnect the battery charger to the positive
terminal and earth point in the same order
as when connecting the donor battery in
the jump-starting procedure
( Y page 313).XRead the battery charger's operating
instructions before charging the battery.312BatteryBreakdown assistance