
heat function can only be activated or deac-
tivated with the ignition switched off.
ECO start/stop function During automatic engine switch-off, the cli-
mate control only operates at a reduced capa- city. If you require full climate control capa-
city, the ECO start/stop function can be
deactivated by pressing the ECO button
(Y page 147). Operating the climate control sys-
tems
Switching climate control on/off
General notes When the climate control is switched off, the
air supply and air circulation are also
switched off. The windows could fog up.
Therefore, switch off climate control only
briefly
i Activate climate control primarily using
the 0058 button (Y page 129).
Air-conditioning system X
Turn the SmartKey to position 2in the igni-
tion lock (Y page 139).
X To activate: turn airflow control 006Bclock-
wise to the desired position (except posi-
tion 0) (Y page 123).
X To deactivate: turn airflow control 006B
counter-clockwise to position
0(Y page 123). Dual-zone automatic climate control X
Turn the SmartKey to position 2in the igni-
tion lock (Y page 139).
X To switch on: press the0058button.
The indicator lamp in the 0058button lights
up. Airflow and air distribution are set to
automatic mode.
or
X Press the 0078button.
The indicator lamp in the 0078button goes
out. The previously selected settings are
restored.
X To switch off: press the0078button.
The indicator lamp in the 0078button lights
up. Activating/deactivating cooling with
air dehumidification
General notes If you deactivate the "Cooling with air-dehu-
midification" function, the air inside the vehi-
cle will not be cooled. The air inside the vehi-
cle will also not be dehumidified. The win-
dows can fog up more quickly. Therefore,
deactivate the cooling with air-dehumidifica-
tion function only briefly.
The "Cooling with air dehumidification" func-
tion is only available when the engine is run-
ning. The air inside the vehicle is cooled and
dehumidified according to the temperature
selected.
Condensation may drip from the underside of the vehicle when it is in cooling mode. This isnormal and not a sign that there is a malfunc-
tion. Operating the climate control systems
127Climate control

Activating/deactivating
X
To activate: press the005Aor0056 but-
ton.
The indicator lamp in the 005Aor0056
button lights up.
X To deactivate: press the005Aor0056
button.
The indicator lamp in the 005Aor0056
button goes out. The "Cooling with air dehu- midification" function has a delayed switch-
off feature. 128
Operating the climate control systemsClimate cont
rol

Problems with the "Cooling with air dehumidification" function
Problem
Possible causes/consequences and
0050
0050Solutions The indicator lamp in
the
005A/0056 button
flashes three times or
remains off. The "Cool-
ing with air dehumidifi-
cation" function cannot
be switched on. Cooling with air dehumidification has been deactivated due to a
malfunction.
X Visit a qualified specialist workshop. Setting climate control to automatic
General notes Automatic mode is only available with 2-zone
automatic air conditioning.
In automatic mode, the set temperature is
maintained automatically at a constant level. The system automatically regulates the tem-
perature of the dispensed air, the airflow and
the air distribution.
The automatic mode functions optimally
when the "Cooling with air dehumidification"
function is activated. If necessary, cooling
with air dehumidification can be deactivated.
If you deactivate the "Cooling with air-dehu-
midification" function, the air inside the vehi- cle will not be cooled. The air inside the vehi-
cle will also not be dehumidified. The win-
dows can fog up more quickly. Therefore,
deactivate the cooling with air-dehumidifica-
tion function only briefly.
Activating/switching X
Turn the SmartKey to position 2in the igni-
tion lock (Y page 139).
X Set the desired temperature.
X To activate: press the0058button.
The indicator lamp in the 0058button lights
up. Automatic air distribution and airflow
are activated. X
To switch to manual mode: press the
008F button.
or
X Press the 0095or0097 button.
The indicator lamp in the 0058button goes
out. Setting the temperature
Air-conditioning system X
Turn the SmartKey to position 2in the igni-
tion lock (Y page 139).
X To increase/reduce: turn control0043
clockwise or counter-clockwise
(Y page 123).
Only change the temperature setting in
small increments. Start at 72 ‡ (22 †).
i If you turn control
0043counter-clockwise
to the lowest temperature setting, air-recir-
culation mode may activate automatically,
depending on the outside temperature.
Dual-zone automatic climate control Different temperatures can be set for the
driver's and front-passenger sides.
X Turn the SmartKey to position 2in the igni-
tion lock (Y page 139).
X To increase/reduce: turn control0043or0084
clockwise or counter-clockwise
(Y page 125). Operating the climate control systems
129Climate control

side is not adopted for the front-passenger
side.
X To switch off: press button00D6.
The indicator lamp in the 00D6button goes
out. The temperature setting for the driv-
er's side is adopted for the front-passenger
side. Defrosting the windshield
General notes You can use this function to defrost the wind-
shield or to defrost the inside of the wind-
shield and the side windows.
Switch off the "Windshield defrosting" func-
tion as soon as the windshield is clear again.
Switching the "Windshield defrosting"
function on/off X
Turn the SmartKey to position 2in the igni-
tion lock (Y page 139).
X To activate: press the0064button.
The indicator lamp in the 0064button lights
up.
The climate control system switches to the
following functions:
R high airflow
R high temperature
R air distribution to the windshield and
front side windows
R air-recirculation mode off
X To deactivate: press the0064button.
The indicator lamp in the 0064button goes
out. The previously selected settings are
restored. Air-recirculation mode remains
deactivated.
or X 2-zone automatic climate control: press
the 0058 button.
The indicator lamp in the 0064button goes
out. Airflow and air distribution are set to
automatic mode. MAX COOL maximum cooling
The MAX COOL function is only available in
vehicles for the USA.
MAX COOL is only operational when the
engine is running. X To activate: press the00C9button.
The indicator lamp in the button lights up.
X To activate: press off-road button 00C9
again.
The indicator lamp goes out. The previously selected settings are restored.
When you activate MAX COOL, climate con-
trol switches to the following functions:
R maximum cooling
R maximum airflow
R air-recirculation mode on Defrosting the windows
Windows fogged up on the inside X
Activate the 005A/0056cooling with air
dehumidification function.
X 2-zone automatic air conditioning: activate
the 0058 mode button.
X If the windows continue to fog up, activate
the 0064 "Windshield defrosting" function.
i You should only select this setting until
the windshield is clear again.
Windows fogged up on the outside X
Activate the windshield wipers.
X Air conditioning: press the 009Cor009B
button.
X 2-zone automatic air conditioning: press
the 008F button until the 009Cor009B
symbol appears in the display.
i You should only select this setting until
the windshield is clear again. Operating the climate control systems
131Climate control

Problems with the rear window defroster
Problem
Possible causes/consequences and
0050
0050Solutions The indicator lamp on
the
006C button
flashes. The rear win-
dow defroster has
deactivated prema-
turely or cannot be acti- vated. The on-board voltage is too low because too many electrical con-
sumers are switched on.
X Switch off any consumers that are not required, e.g. reading
lamps, interior lighting or the seat heating.
When the battery is sufficiently charged, the rear window
defroster can be activated again. The roof is open.
X Close the roof.
When the roof is closed, the rear window defroster can be acti-
vated again. Activating/deactivating air-recircula-
tion mode
General notes If you switch on air-recirculation mode, the
windows can fog up more quickly, in particu-
lar at low temperatures. Only use air-recircu-
lation mode briefly to prevent the windows
from fogging up.
Activating/deactivating X
Turn the SmartKey to position 2in the igni-
tion lock (Y page 139).
X To activate: press the0072button.
The indicator lamp in the 0072button lights
up.
i Air-recirculation mode is automatically
activated at high levels of pollution (dual-
zone automatic climate control only) or at
high outside temperatures. When air-recir-
culation mode is activated automatically,
the indicator lamp in the 0072button is not
lit. Outside air is added after about
30 minutes.
X To deactivate: press the0072button.
The indicator lamp in the 0072button goes
out. i
Air-recirculation mode deactivates auto-
matically:
R after approximately five minutes at out-
side temperatures below approximately
41 ‡ (5 †)
R after approximately five minutes if cool-
ing with air dehumidification is deactiva-
ted
R after approximately 30 minutes at out-
side temperatures above approximately
41 ‡ (5 †) if the "Cooling with air dehu-
midification" function is activated Activating/deactivating the residual
heat function
General notes The residual heat function is only available on
vehicles for Canada.
It is possible to make use of the residual heat
of the engine to continue heating the station- ary vehicle for up to 30 minutes after the
engine has been switched off. The heating
time depends on the temperature that has
been set.
Depending on the equipment level, the con-
trol panel has either the 004Bbutton or the
0056 button. Operating the climate control systems
133Climate control

Display messages
Possible causes/consequences and
0050
0050Solutions 0049
Auto Auto
Lamp
LampFunction
Function
Inoperative
Inoperative The light sensor is defective.
X Visit a qualified specialist workshop. 0049
Switch Off Lights Switch Off Lights The lights are still switched on when you leave the vehicle. A
warning tone also sounds.
X Turn the light switch to 0058.Adaptive Highbeam Adaptive Highbeam
Assist Inoperative Assist Inoperative Adaptive Highbeam Assist is faulty.
X
Visit a qualified specialist workshop. Adaptive Highbeam Adaptive Highbeam
Assist Currently Assist Currently
Unavailable See Unavailable See
Operator's Manual Operator's Manual Adaptive Highbeam Assist is deactivated and temporarily inoper-
ative. Possible causes are:
R the windshield in the camera's field of vision is dirty.
R visibility is impaired due to heavy rain, snow or fog.
X Clean the windshield.
If the system detects that the camera is fully operational again, the
Adaptive Highbeam Assist Now Available
Adaptive Highbeam Assist Now Available message is dis-
played.
Adaptive Highbeam Assist is operational again. Engine
Display messages
Possible causes/consequences and
0050 0050Solutions 00BD
Check Coolant Check Coolant
Level See Opera‐ Level See Opera‐
tor's Manual tor's Manual The coolant level is too low.
! Avoid making long journeys with too little coolant in the engine
cooling system. The engine will otherwise be damaged.
X Add coolant, observing the warning notes before doing so
(Y page 281).
X If coolant needs to be added more often than usual, have the
engine coolant system checked at a qualified specialist work-
shop. 00AC The fan motor is faulty.
X At coolant temperatures below 248 ‡ (120 †), drive to the
nearest qualified specialist workshop.
X Avoid subjecting the engine to heavy loads, e.g. driving in moun-
tainous terrain, and stop-and-go traffic. 228
Display
messagesOn-board computer and displays

X
Replace cap 0043on the filler neck and turn
clockwise.
Ensure that the cap locks into place
securely.
X Check the oil level again with the oil dip-
stick (Y page 279).
Further information on engine oil
(Y page 349). Checking and adding other service
products
Checking coolant level G
WARNING
Certain components in the engine compart-
ment, such as the engine, radiator and parts
of the exhaust system, can become very hot.
Working in the engine compartment poses a
risk of injury.
Where possible, let the engine cool down and touch only the components described in the
following. G
WARNING
The engine cooling system is pressurized, par- ticularly when the engine is warm. When
opening the cap, you could be scalded by hotcoolant spraying out. There is a risk of injury.
Let the engine cool down before opening the
cap. Wear eye and hand protection when
opening the cap. Open the cap slowly half a
turn to allow pressure to escape. Example X
Park the vehicle on a level surface.
Only check the coolant level when the vehi- cle is on a level surface and the engine has
cooled down.
X Turn the SmartKey to position 2in the igni-
tion lock (Y page 139).
On vehicles with KEYLESS-GO, press the
Start/Stop button twice (Y page 140).
X Check the coolant temperature gauge in
the multifunction display.
The coolant temperature must be below
158 ‡ (70 †).
X Turn the SmartKey to position
0(Y page 139) in the ignition lock.
X Slowly turn cap 0044half a turn counter-
clockwise to allow excess pressure to
escape.
X Turn cap 0044further counter-clockwise and
remove it.
If the coolant is at the level of marker bar 0087
in the filler neck when cold, there is enough coolant in coolant expansion tank 0043.
If the coolant level is approximately 0.6 in
(1.5 cm) above marker bar 0087in the fuel
filler neck when warm, there is enough
coolant in expansion tank 0043.
X If necessary, add coolant that has been tes-
ted and approved by Mercedes-Benz.
X Replace cap 0044and turn it clockwise as far
as it will go.
For further information on coolant, see
(Y page 351).
Windshield washer system G
WARNING
Certain components in the engine compart-
ment, such as the engine, radiator and parts
of the exhaust system, can become very hot.
Working in the engine compartment poses a
risk of injury.
Where possible, let the engine cool down and touch only the components described in the
following. Engine compartment
281Maintenance and care Z

Coolant
Important safety notes G
WARNING
If antifreeze comes into contact with hot com- ponents in the engine compartment, it may
ignite. There is a risk of fire and injury.
Let the engine cool down before you add anti-
freeze. Make sure that antifreeze is not spilled
next to the filler neck. Thoroughly clean the
antifreeze from components before starting
the engine.
! Only add coolant that has been premixed
with the desired antifreeze protection. You
could otherwise damage the engine.
Further information on coolants can be
found in the Mercedes-Benz Specifications for Service Products, MB BeVo 310.1, e.g.
on the Internet at
http://bevo.mercedes-benz.co m.Or con-
tact a qualified specialist workshop.
! Always use a suitable coolant mixture,
even in countries where high temperatures prevail.
Otherwise, the engine cooling system is not
sufficiently protected from corrosion and
overheating.
i Have the coolant regularly replaced at a
qualified specialist workshop and the
replacement confirmed in the Maintenance Booklet.
Comply with the important safety precautions for service products when handling coolant
(Y page 347).
The coolant is a mixture of water and anti-
freeze/corrosion inhibitor. It performs the
following tasks:
R corrosion protection
R antifreeze protection
R raising the boiling point
If the coolant has antifreeze protection down to -35 ‡(-37 †), the boiling point of the cool- ant during operation is approximately 266 ‡
(130 †).
The antifreeze/corrosion inhibitor concentra- tion in the engine cooling system should:
R be at least 50%. This will protect the engine
cooling system against freezing down to
approximately -35 ‡(-37 †).
R not exceed 55% (antifreeze protection
do wn to -49 ‡ [-45 †]). Otherwise, heat
will not be dissipated as effectively.
If the vehicle has lost coolant, add equal
amounts of water and antifreeze/corrosion
inhibitor.
Mercedes-Benz recommends an antifreeze/
corrosion inhibitor concentrate in accord-
ance with MB Specifications for Service Prod-
ucts 310.1.
i When the vehicle is first delivered, it is fil-
led with a coolant mixture that ensures
adequate antifreeze and corrosion protec-
tion.
i The coolant is checked with every main-
tenance interval at a qualified specialist
workshop.
Filling capacities Missing values were not available at time of
going to print.
Model Capacity
SLK 250
Approx. 10.1 US qt
(9.6l) SLK 350
Approx. 11.0 US qt
(10.4l) SLK 55 AMG
i
Use MB 325.0 or MB 326.0 approved
antifreeze/corrosion inhibitor. Service products and filling capacities
351Technical data Z