First read and observe the introductory information
and safety warnings 
The auxiliary heater exhaust system, located under the vehicle, must not be blocked by snow, mud or other items. The exhaust fumes must not be obstructed in any way. The emissions generated by the auxiliary heater are removed via an exhaust pipe fitted underneath the vehicle.
When the vehicle interior is being heated, the warm air is first directed towards the windscreen and then via the air vents to the vehicle interior. This is dependent on the ambient temperature. You can determine the flow of the air by adjusting the position of the vents, for example to face the side windows.
When is the auxiliary heater not switched on?
Operating noises can be heard if the auxiliary heater is switched on.
At high levels of humidity in the outside air, but at low temperatures, condensation from the heating and fresh air system may evaporate through the active auxiliary heater. If this is the case, steam may appear underneath the vehicle. The vehicle is not damaged.
When the vehicle is parked at a steep angle, e.g. on an upward or downward incline, the auxiliary heater function may impaired if the fuel tank level is low (just above the reserve quantity).
The vehicle battery will discharge if the auxiliary heater runs several times in an extended period. Drive the vehicle for an appropriate distance in order to recharge the vehicle battery. As a rule of thumb, drive the vehicle for the length of time you ran the system.
Removing and installing onboard supply control unit -J519-, LHD vehicles
Note
When renewing the control unit, select
Renew function for the respective control unit in
Guided fault finding or
Guided functions mode
→ Vehicle
diagnostic tester.
Removing
â ...
Removing and installing refrigerant shut-off valve for high-voltage battery
heat exchanger -N542
Removing
–
Observe safety precautions
→ Chapter „Safety precautions when handling refrigerants“.
–
Comply with notes
→ Chapter „Working on refrigerant circuit“.
...
Repairing lock carrier. Left headlight mounting
Note
Line -2- indicates the position
where the tab might break off.
–
Remove front bumper cover
→ Chapter.
–
Remove headlights
→ Electrical system; Rep. gr.94.
–
...