
 
Maximum heat output and the fastest possible defrosting of the windows are possible only when 
the engine is running. Do not start your journey until you have good visibility. 
To help ensure good visibility, make sure that you use the air conditioning system and the rear 
window heating correctly. 
Auxiliary heater and ventilation 
 Introduction 
This chapter contains information on the followingsubjects: 
Switching the auxiliary heater and ventilation on and off
Programming the auxiliary heater and ventilation
Remote control
The auxiliary heater and ventilation system can be used to heat the vehicle interior in the winter and 
ventilate it in the summer. It is able to clear ice, condensation and a thin layer of snow from the 
windscreen. The auxiliary heater is supplied with fuel from the vehicle fuel tank and can be operated 
when the vehicle is stationary with the ignition switched off. The auxiliary ventilation system is 
powered by the 12-volt vehicle battery. 
Auxiliary heater exhaust system 
The emissions generated by the auxiliary heater are discharged via an exhaust pipe underneath the 
vehicle. The exhaust pipe must not be blocked by snow, mud or other objects. 
 
WARNING 
Among other things, the emissions from the auxiliary heater contain carbon monoxide, which is an 
odourless and colourless poisonous gas. Carbon monoxide can cause people to lose consciousness. It 
can also cause death. 
Never switch on the auxiliary heater when the vehicle is in unventilated or closed rooms nor let the 
auxiliary heater run in unventilated or closed rooms. 
Never program the auxiliary heater so that it is switched on and runs in unventilated or closed 
rooms. 
 
WARNING 
Parts of the auxiliary heater exhaust system become very hot. This can cause fires. 
Park the vehicle so that no part of the exhaust system can come into contact with any inflammable 
material underneath the vehicle, e.g. dry grass. 
  

 
Food, medicine and other items that are sensitive to heat or cold could be either damaged or 
rendered useless by the air flowing out of the vents. 
Never leave food, medicines or other temperature-sensitive objects in front of the vents. 
Switching the auxiliary heater and ventilation on and off 
First read and observe the introductoryinformation and safety warnings
The auxiliary heater can be operated only when the ignition is switched off. If the ignition is switched 
on while the auxiliary heater is working, the auxiliary heater continues to run to provide additional 
heat. 
Switching on the auxiliary heater 
Press the immediate heat button in the air conditioning block Front controls 
OR: press the button on the remote control Remote control 
OR: program the departure time Programming the auxiliary heater and ventilation 
The auxiliary heater heats the vehicle interior to at least 22  
The auxiliary heater will not switch on if the 12-volt vehicle battery is low or the fuel tank is empty. 
Switching off the auxiliary heater manually 
Press the immediate heat button in the air conditioning block Front controls 
OR: press the button on the remote control Remote control 
OR: touch the function button on the Infotainment system Programming the auxiliary heater 
Auxiliary heater switches off automatically 
When the programmed departure time is reached, or after the programmed operating period has 
elapsed Programming the auxiliary heater and ventilation 
When the indicator lamp lights up (fuel gauge) Fuel gauge 
If the charge level of the 12-volt vehicle battery is too low 12-volt vehicle battery 
The auxiliary heater runs on for a short time after it has been switched off manually or automatically 
so that the remaining fuel in the system can be burnt off. 
 
When the vehicle is at a standstill, the auxiliary heater can be activated up to three times in 
succession for the maximum operating duration. 
  

 
 
The 12-volt vehicle battery will discharge if the auxiliary heating or ventilation is run several times 
over an extended period. Drive the vehicle for an appropriate distance in between in order to 
recharge the 12-volt vehicle battery. 
 
The fuel gauge indication may not be accurate (just above the reserve quantity) when the vehicle is 
parked on a slope; this may restrict the function of the auxiliary heater. 
 
The auxiliary heater may switch on automatically when the engine is started at temperatures below 
+5

e date and time set in the vehicle are correct Time 
Open the Auxiliary heater menu. 
Touch the Set function button. 
Select one of the memory locations for a Departure time. 
Touch the Activate function button. 
Manual air conditioning system: the programmed departure time determines the time at which 
the auxiliary heater or ventilation should switch off. The point at which the heating or ventilation 
process starts is determined depending on the programmed running time. 
Climatronic: on the basis of the programmed departure time, the vehicle automatically 
calculates the start time for heating or ventilation to the currently set temperature depending on 
the outside temperature. 
Press the Running time function button under Adjust in order to select the running time when the 
auxiliary heater is switched on using the immediate heat button  or remote control. 
Checking programming 
If a departure time has been activated, the LED in the immediate heat button  will light up on the 
Climatronic control panel for approximately 10 seconds after the ignition is switched off. 
 
WARNING 
Never program the auxiliary heating system so that is switched on and run in unventilated or 
enclosed spaces. Among other things, the emissions from the auxiliary heater contain carbon 
monoxide, which is an odourless and colourless poisonous gas. Carbon monoxide can cause people 
to lose consciousness. It can also cause death. 
Remote control 
 
Fig. 93 Auxiliary heater: remote control (left) with battery compartment (right). 
First read and observe the introductoryinformation and safety warnings 

 
Switching on: press the  button Fig. 93 
The auxiliary heater is switched on when the LED on the remote control is lit up green. 
Switching off: press the  button Fig. 93 
The auxiliary heater is switched off when the LED on the remote control is lit up red. 
LED in the remote control 
The LED Fig. 93 
Lit up 
greenThe auxiliary heater is switched on.redThe auxiliary heater is switched off. 
Flashing irregularly 
greenAuxiliary heater disabled: the fuel tank is nearly empty, the 12-volt vehicle battery voltage is 
too low or a malfunction has occurred. Refuel and drive long enough to recharge the 12-volt vehicle 
battery or visit a qualified workshop. 
Flashing regularly 
red or greenSwitch-on or switch-off signal has not been received. Move closer to the vehicle. 
Lit up or flashing 
orangeThe button cell (battery) in the remote control is weak. Replace the button cell. 
Range 
The remote control has a range of a few hundred metres when the button cell is fully charged. 
Maintain a distanced of at least 2 metres between the remote control and the vehicle. 
Avoid any obstacles between the remote control and the vehicle. 
Hold the remote control with the aerial Fig. 93pointing vertically upwards. 
Do not cover the aerial. 
Adverse weather or a weak battery cell will significantly reduce the range. 
Renewing the button cell in the remote control 
The button cell in the remote control must be replaced if the indicator lamp does not light up. 
Insert a suitable object, e.g. a screwdriver, in the recess on the side in the direction of the arrow 
Fig. 93 
Use the object to lever off the battery cover. 
Slide the battery cover forwards slightly in the direction of the arrow.  

Fig. 192 Battery window on the top of the 12-volt vehicle battery (illustration). 
First read and observe the introductoryinformation and safety warnings
The electrolyte level of the 12-volt vehicle battery should be checked regularly in high-mileage 
vehicles, in hot countries and in older 12-volt vehicle batteries. The 12-volt vehicle battery is 
otherwise maintenance-free. 
Vehicles with an auxiliary heater Auxiliary heater and ventilationare fitted with special vehicle 
batteries. The electrolyte level of these 12-volt vehicle batteries cannot be checked for technical 
reasons. Go to a qualified workshop to have the 12-volt vehicle battery checked. 
Preparations 
eparing the vehicle for working in the engine compartment In the engine compartment 
 In the engine compartment 
Checking the electrolyte level (12-volt vehicle batteries with battery window) 
e for you to clearly see the colour indicator in the round 
battery window on the top of the 12-volt vehicle battery Fig. 192(arrow). Never use naked 
flames or glowing objects as a light source. 
s according to the electrolyte level in the 
12-volt vehicle battery. 
Light yellow or without colourThe electrolyte level of the 12-volt vehicle battery is too low. The 12-
volt vehicle battery should be checked and replaced by a qualified workshop if necessary.BlackThe 
electrolyte level of the 12-volt vehicle battery is correct. 
 
WARNING 
Any work on the 12-volt vehicle battery can cause serious chemical burns, explosions and electric 
shocks. 
  

-volt vehicle battery 
-volt vehicle 
battery. 
e cable and then the negative cable  
Various indicator lamps may light up after the 12-volt vehicle battery has been connected and the 
ignition is switched on. They will go out when you drive a short distance at a speed of approximately 
15 20 km/h (10 12 mph). If the indicator lamps remain lit up, the vehicle should be checked by a 
qualified workshop. 
If the 12-volt vehicle battery was disconnected for an extended period, the system may not able to 
calculate or correctly display the time when the next service is due Instrument cluster
the maximum permissible service intervals Service 
Automatic switch-off for electrical consumers 
The intelligent vehicle electrical system management function automatically implements a range of 
measures to prevent the 12-volt vehicle battery from discharging under high loads: 
 
 
power supply to the 12-volt socket and the cigarette lighter may be interrupted temporarily 
while the engine is being started. 
The vehicle electrics management system cannot always prevent the 12-volt vehicle battery from 
being discharged, for example if the ignition is left on over a long period with the engine off or the 
side lights or parking lights are left on over a long period of time. 
12-volt vehicle battery is discharged 
gnition is switched on. 
 
Auxiliary heater and ventilation 
 
WARNING 
Incorrectly mounting the battery and using incorrect 12-volt vehicle batteries can cause short 
circuits, fire and serious injuries. 
-free and leak-proof 12-volt vehicle batteries that have the same 
properties, specifications and dimensions as the factory-fitted 12-volt vehicle battery. 
 
WARNING 
A highly explosive mixture of gases is given off when the 12-volt vehicle battery is being charged.