Enabling and disabling the automatic mode of the climate control system in the Mercedes-Benz W203

Automated heating system (Heizmatic) 
1 - Control panel 
2 - Air supply adjusting wheel for left middle vent 
3 - Rotatable middle vent, left 
4 - Cold air mixing adjusting wheel for middle vents, side vents and air vent on instrument panel, top and middle vents in the rear (on models with automated Thermatic or Thermotronic HF) 
5 - Rotatable middle vent, right 
6 - Air supply adjustment wheel for the right middle vent 
7 - Ventilation deflector on the instrument panel, from above, with air supply adjustment wheel 
8 - Air supply adjustment wheel for side deflector 
9 - Rotatable side deflector 
10 - Side window defrost deflector

Control panel 
1 - Rotary air supply switch 
2 - Temperature control for left side 
3 - Temperature control for right side 
4 - Air distribution control 
5 - Window defrost 
6 - Switch to air circulation mode, engine residual heat recovery mode on suitably equipped models 
7 - Rear window heater

The set temperature is reached in the heating mode as quickly as possible and maintained constant. The temperature can be set for each side separately. 
Change the set temperature only in small steps, otherwise the plastic gears of the damper mechanisms will quickly grind off.
Models with Residual Engine Heat Function: 
When using the Residual Engine Heat Function, the vehicle interior can also be heated when the engine is off. 
We recommend setting the thermostats to 22°C as a basic setting for interior temperature control. 

General notes on automated heating system The 

dust filter completely retains pollen and dust particles up to a certain value. 
If the passenger compartment is heated by the sun, air it out quickly before driving. 
Do not block the air vents in the space between the rear seat backrest and the rear window. 
Keep the air inlets on the hood clear of snow.
Manual air distribution control Air 
distribution control is carried out simultaneously for the left and right sides. 

Air outlet at the top from the middle and side vents, as well as from the vents on the instrument panel. 

 Air outlet from windshield vents and side window defrost vents. 

Air outlet from footwell vents, center and side vents and rear footwell vents.

Basic position of the controls in heating mode (in winter) 
Set the temperature controllers (2 and 3) as desired. 
Set the air supply regulator as desired, but not less than position 2, otherwise the windows may fog up. 
Install the air distribution regulator (4) as shown in the illustration above. 
To reduce the temperature in the space under the ceiling, open the adjusting wheel for mixing cold air as desired. 

Open the middle and side vents as desired.
Basic position of the controls in ventilation mode (summer) 
Set the temperature controllers (2 and 3) as desired. 
Set the air supply regulator (1) as desired, but not less than position 1. 

Turn the air distribution regulator (4) to . 

Open the middle deflectors. 
Open the side deflectors. 
In order to evenly distribute air, open the ventilation deflector on the top of the instrument panel. 

With this installation, good ventilation of the cabin is ensured. 
Special positions - select only for a short time 
Switching off and on the automatic heating system
Turn the air supply rotary switch to 0. 
To switch on the automatic heating system, turn the air supply rotary switch to the desired fan position. 

Defrosting windows 

Press the button  . The control LED on the button lights up. 
If necessary, switch off the air circulation mode  . The control LED on the button goes out.

Windows fogging up from the inside 

Switch off the air circulation mode (6) if necessary. The control LED on the button goes out. 
Turn the air distribution regulator (4) to position  . 
Set the air supply regulator (1) to a higher fan stage. 
Set the temperature controllers (2 and 3) to a higher temperature.
Penetration of unpleasant odors from the outside into the passenger compartment 

Switch on the air circulation mode only for a short time, otherwise the windows may fog up. 
Switch on the air circulation mode: press the button  . The control LED on the button lights up. 
The air circulation mode will automatically turn off after about 5 minutes.

Engine residual heat utilization mode 

With the engine switched off, interior heating is still possible for some time. The duration of heating depends on the set temperature. 
Set both temperature controls as desired. 
Set the air distribution through the ventilation deflectors as desired. 
Regardless of the position of the air supply regulator, the fan operates at a low level. 
Before switching on: turn the key in the ignition switch to position 1 or 0 or remove it. 

Switching on the mode of using the residual heat of the engine 

Press the button  . The control LED on the button lights up. 

Switching on is not possible if the battery is not sufficiently charged. 

Disabling the use of the residual heat of the engine 

Click on the button  . 
The control LED does not go out. 
Automatic switch-off takes place: 

· if the ignition key is turned to position 2, 
· after approx. 30 minutes, 
· if the battery voltage drops.

Source: http://www.w203club.com/viewtopic.php?p=1069