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XPull protective cap:in the direction of the
arrow, out of the ball coupling recess.
XStow protective cap :so that it cannot be
thrown around.
Observe the loading guidelines
(
Ypage 306) and the safety notes regard-
ing stowage spaces (
Ypage 306).
XInsert the ball coupling horizontally into ball coupling recess ;in the direction of the
arrow until the holes in ball coupling =are
in line with the holes in ball coupling
recess ?.
XSlide bolt Ainto the hole in the ball cou-
pling recess and the ball coupling to the
stop.
XSecure the bolt using spring cotter B.
XCheck the ball coupling, bolt and spring
cotter for correct installation.
If the ball coupling cannot be correctly moun- ted, remove the ball coupling. Under these
circumstances, the ball coupling must not be
used for trailer towing.
If the ball coupling cannot be locked and the
key cannot be removed, remove the ball cou- pling and clean it. If the ball coupling can still
not be installed (locked) after it has been
Towing a trailer231
Driving and parking
Z
Page 234 of 418

cleaned, remove the ball coupling. The trailer
tow hitch must then not be used to tow a
trailer, as safe operation cannot be guaran-
teed.
Have the entire trailer tow hitch checked at a
qualified specialist workshop.
Coupling up a trailer
!
Do not connect the trailer's brake system
(if featured) to the hydraulic brake system
of the towing vehicle, as the latter is equip-
ped with an anti-lock brake system. Doing
so will result in a loss of function of the
brake systems of both the vehicle and the
trailer.
XShift the transmission to position P.
XApply the vehicle's electric parking brake.
XStart the engine.
XVehicles with AIR BODY CONTROL:
selectComfort driving program or Trailer
off-road program.
XSwitch off the engine.
XClose the doors and tailgate.
XCouple up the trailer.
XEstablish the electrical connection
between the vehicle and the trailer.
XCheck that the trailer lighting system is
working.
XPush the combination switch upwards/
downwards and check whether the corre-
sponding turn signal on the trailer flashes.
A trailer that is connected is recognized only
when the electrical connection is established
correctly and when the lighting system is
working properly. The function of other sys-
tems also depends on this, for example:
RESP®
RPARKTRONIC
RActive Parking Assist
RActive Blind Spot Assist
RActive Lane Keeping Assist
iVehicles with AIR BODY CONTROL: if you
couple up a trailer, the vehicle always
remains at highway level. When coupling up
a trailer, please observe the following:
RUnless highway level has been set man-
ually, the vehicle is automatically low-
ered to highway level. This is the case if a
speed of 5 mph (8 km/h) is reached.
These restrictions apply to all accessories
powered through a connection to the trailer
power socket of your vehicle, e.g. a bicycle
carrier.
Observe the maximum permissible trailer
dimensions (width and length).
Most U.S. states and all Canadian provinces
require by law:
RSafety chains between the towing vehicle
and the trailer. The chains should be cross-
wound under the trailer drawbar. They must
be fastened to the vehicle's trailer cou-
pling, not to the bumper or the axle.
Leave enough play in the chains to make
tight cornering possible.
RA separate brake system for certain types
of trailer.
RSafety switch for braked trailers. Check the specific legal requirements applicable to
your state.
If the trailer becomes detached from the
towing vehicle, the safety switch applies
the trailer brakes.
Towing a trailer
There are numerous legal requirements con-
cerning the towing of a trailer, e.g. speed
restrictions. Make sure that your car/trailer
combination complies with the local regula-
tions:
Rin your place of residence
Rin the location to which you are driving
The police and local authorities can provide
reliable information.
232Towing a trailer
Driving and parking
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Observe the following when towing a trailer:
RTo gain driving experience and to become
accustomed to the new handling charac-
teristics, you should practice the following
in a traffic-free location:
-cornering
-stopping
-backing up
RBefore driving, check:
-trailer tow hitch
-safety switch for braked trailers
-safety chains
-electrical connections
-lights
-wheels
RAdjust the exterior mirrors to provide an
unobstructed view of the rear section of the
trailer.
RIf the trailer has electronically controlled
brakes, pull away carefully. Brake manually
using the brake controller and check
whether the brakes function correctly.
RSecure any objects on the trailer to prevent
the cargo from slipping when the vehicle is
in motion.
RWhen you couple up a trailer, check at reg-
ular intervals that the load is firmly secured.
If the trailer is equipped with trailer lights
and brakes, check the trailer to ensure that
these are working.
RBear in mind that the handling will be less
stable when towing a trailer than when driv-
ing without one. Avoid sudden steering
movements.
RThe vehicle/trailer combination is heavier,
accelerates more slowly, has a decreased
gradient climbing capability and a longer
braking distance.
It is more susceptible to side winds and
requires more careful steering.
RIf possible, do not brake suddenly, but
instead depress the brake pedal moder-
ately at first so that the trailer can activate its brakes. Then increase the pressure on
the brake pedal.
RIf the automatic transmission repeatedly
shifts between gears on uphill or downhill
gradients, shift to a lower gear using the
left-hand steering wheel paddle shifter.
A lower gear and lower speed reduce the
risk of engine failure.
RWhen driving downhill, shift to a lower gear
to utilize the engine's braking effect.
Avoid continuous brake application as this
may overheat the vehicle brakes and, if
installed, the trailer brakes.
RIf the coolant temperature increases dra-
matically while the air-conditioning system is switched on, switch off the air-condition-
ing system.
Coolant heat can also be dissipated by
opening the windows and switching the
ventilation blower and the interior temper-
ature to the highest level.
RWhen overtaking, pay particular attention
to the extended length of your vehicle/
trailer combination.
Due to the length of the vehicle/trailer
combination, you require addi
tional road
space in relation to the vehicle you are
overtaking before you can change back to
the original lane.
Decoupling a trailer
GWARNING
If you uncouple a trailer with the overrun
brake engaged, you could trap your hand
between the vehicle and the trailer drawbar.
There is a risk of injury.
Do not uncouple a trailer if the overrun brake
is engaged.
!Do not disconnect a trailer with an
engaged overrun brake. Otherwise, your
vehicle could be damaged by the rebound-
ing of the overrun brake.
Towing a trailer233
Driving and parking
Z
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XMake sure that the automatic transmissionis set to position P.
XApply the vehicle's parking brake.
XClose all doors and the tailgate.
XApply the trailer's parking brake.
XRemove the trailer cable and decouple the
trailer.
Removing the ball coupling
XRemove the spring cotter.
XRemove the bolt from the ball coupling
recess.
XRemove the ball coupling from the ball cou-
pling recess.
XClean the ball coupling if it is dirty.
XStow the ball coupling so that it cannot be
thrown around.
Observe the loading guidelines (
Ypage 306)
and the safety notes regarding stowage
spaces (
Ypage 306).
Information on cleaning and care of the trailer
tow hitch (
Ypage 349).
Trailer power supply
The trailer socket of your vehicle is equipped
at the factory with a permanent power supply.
The permanent power supply is supplied via
trailer socket pin 4.
!Accessories with a maximum power con-
sumption of 180 W can be connected to the
permanent power supply.
You must not charge a trailer battery using
the power supply.
The trailer's permanent power supply is
switched off in the event of low vehicle supply
voltage and after six hours at the latest.
A qualified specialist workshop can provide
more information about installing the trailer
electrics.
Permissible trailer loads and trailer
drawbar noseweights
Weight specifications
The gross trailer weight is calculated by add-
ing the weight of the trailer to the weight of
the load and equipment on the trailer.
You will find installing dimensions and loads
under "Technical data" (
Ypage 415).
Loading a trailer
RWhen loading the trailer, make sure that
neither the permissible gross weight of the
trailer nor the gross vehicle weight is
exceeded. The permissible gross vehicle
weight is indicated on the identification
plate on the B-pillar on the driver's side of
the vehicle.
You can find the maximum permissible val-
ues on the type plates of your vehicle and
the trailer. When calculating how much
weight the vehicle and trailer may carry,
pay attention to the respective lowest val-
ues.
RThe trailer drawbar load on the ball coupling
must be added to the rear axle load to avoid
exceeding the permissible gross axle
weight. The permissible gross vehicle
weight is indicated on the identification
plate on the B-pillar on the driver's side of
the vehicle.
iMercedes-Benz recommends a trailer
load where the trailer drawbar noseweight
accounts for 8% to 15% of the trailer's per-
missible gross weight.
iThe weight of other accessories, passen-
gers and loads reduces:
Rthe permissible trailer load
Rthe permissible noseweight that your
vehicle can tow
234Towing a trailer
Driving and parking
Page 237 of 418
Checking the vehicle and trailer weight
RTo ensure compliance of the weight of the
towing vehicle and the trailer with the max-
imum permissible values, have the vehicle/
trailer combination (towing vehicle includ-
ing driver, passenger, load and fully laden
trailer) weighed on a calibrated weigh-
bridge.
RCheck the gross axle weight rating of the
front and rear axles, the gross weight of the
trailer and trailer drawbar load.
Towing a trailer235
Driving and parking
Z
Page 238 of 418
Page 239 of 418
Useful information............................238
Important safety notes .....................238
Displays and operation .....................238
Menus and submenus ......................243
Display messages ............................. 257
Warning and indicator lamps in the
instrument cluster ............................291
237
On-board computer and displays
Page 240 of 418

Useful information
i
This Operator's Manual describes all
models and all standard and optional equip-
ment 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.
iRead the information on qualified special-
ist workshops (
Ypage 27).
Important safety notes
GWARNING
If you operate information systems and com-
munication equipment integrated in the vehi-
cle while driving, you will be distracted from
traffic conditions. You could also lose control
of the vehicle. There is a risk of an accident.
Only operate the equipment when the traffic
situation permits. If you are not sure that this
is possible, park the vehicle paying attention
to traffic conditions and operate the equip-
ment when the vehicle is stationary.
You must observe the legal requirements for
the country in which you are currently driving
when operating the on-board computer.
GWARNING
If the instrument cluster has failed or mal-
functioned, you may not recognize function
restrictions in systems relevant to safety. The
operating safety of your vehicle may be
impaired. There is a risk of an accident.
Drive on carefully. Have the vehicle checked
at a qualified specialist workshop immedi-
ately.
If the operating safety of your vehicle is
impaired, pull over as soon as it is safe to do
so. Contact a qualified specialist workshop. The on-board computer only shows messages
or warnings from certain systems in the mul-
tifunction display. You should therefore make
sure your vehicle is operating safely at all
times.
For an overview, see the instrument panel
illustration (
Ypage 33).
Displays and operation
Instrument cluster lighting
The lighting in the instrument cluster, in the
displays and the controls in the vehicle inte-
rior can be adjusted using brightness control
knob
:.
XTurn brightness control knob :up or
down.
If you turn the light switch (
Ypage 124) to
the T, ÃorL position, the
brightness will depend upon the brightness
of the ambient light.
iThe light sensor in the instrument cluster
automatically controls the brightness of
the multifunction display.
In daylight, the displays in the instrument
cluster are illuminated. A dimming function
is not possible in daylight.
Speedometer with segments
The speedometer is divided into segments on vehicles with DISTRONIC PLUS.
238Displays and operation
On-board computer and displays