Mercedes S-Class W-140

1991-1999 of release

Repair and operation of the car



Mercedes S-Class
+ Mercedes-Benz cars of the class S (W-140)
+ Operation manual
+ Routine maintenance
+ Engine
- Cooling systems, heating
   Specifications
   + Engine cooling system
   - Systems of ventilation, heating and air conditioning
      Casing of the fan and ventilatory assembly - installation details (on the example of petrol model with the engine of the M120.980/982 series)
      The air conditioning system - additional information and precautionary measures
      Arrangement of basic elements of the automatic air conditioning system
+ Power supply system and release
+ Engine electric equipment
+ Gear shifting box
+ Automatic transmission
+ Coupling
+ Brake system
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment






Systems of ventilation, heating and air conditioning

See also Section Comfort of the Head Operation Manual

The air given by system of ventilation to interior of the car via the filter can be warmed up or cooled depending on the choice of the driver and passengers. The heater or the conditioner settle down in salon, in the case under the dashboard. All stream of the air given to salon goes for heating or cooling through the same casing. Temperature and speed of a stream of air is regulated by means of the governing bodies located on the control panel.

Scheme of the cooling system

1 — the Broad tank
2 — the Cover
3 — the Built-in silikogelevy tank
4 — the Intaking branch pipe
5 — the Radiator
6 — the Thermostat
7 — the Ventilating tube
8 — the Stream from the engine to a radiator
9 — the Stream from a radiator to the engine
10 — the cooling system Pump

11 — the Oil heater
12 — the Block of cylinders
13 — the Head of the block of cylinders
14 — the Forcing heater pipeline
15 — the Heater of windscreen washers
16 — a heater Radiator
17 — the Valve of a double pulsation
18 — the Circulation pulser
19 — the Returnable tube of a heater

Heat generated during the operation of the engine is transferred by cooling liquid to the heater radiator located in salon. The brought air stream from system of ventilation passes through a radiator and heats up heat of the cooling liquid of the engine proceeding in a radiator. Extent of heating is regulated by means of mixing in a certain ratio of cold and hot air by means of the mixing gate with the servo-driver.

The used air is removed from salon through air vents with backpressure valves.

Increase in a consumption of air via the heat exchanger provides the fan of fresh air.

If it is necessary to turn off supply of fresh air, for example, at a bad smell, the system switches in the circulation mode at which in salon only the air which is available there circulates.

Switching of system in the mode of circulation is confirmed by activation of a control lamp (see the Head the Operation manual).

Air conditioning system of salon

Functional schemes of the typical air conditioning system

Working path of a forward contour of the K/V system

And — the Entrance opening of cooling liquid
In — the Return stream of cooling liquid
1 — the Engine
2 — the Block of pumping of heating of salon

3 — the Heat exchanger of a heater of salon
6 — the Radiator of heating of a windshield (screen wiper)
7 — the Thermal valve, heating of a windshield (screen wiper)
8 — the Thermal valve, a liquid heater for washing of a windshield


Working path of a back contour of the K/V system

And — the Input of cooling liquid
In — the Return stream of cooling liquid
1 — the Engine
2 — the Block of pumping of heating of salon
3 — the Heat exchanger, a heating system

4 — the pumping Block, climate control of a back part of salon
5 — the heater Heat exchanger, climate control of a back part of salon
6 — the Radiator of heating of a windshield (screen wiper)
7 — the Thermal valve, heating of a windshield (screen wiper)
8 — the Thermal valve, a liquid heater for washing of a windshield


Works with air conditioning system have to be performed by a specialized workshop. Do not open at all a coolant circulation contour as at contact with skin coolant can cause a frostbite.

By means of air conditioning system air temperature in salon can go down below external temperature.

During the work of system humidity in salon decreases. During wet weather, the arriving fresh air previously it is cooled then again heats up to the set temperature. Thus its drainage is made. By means of this procedure fogging of glasses is removed.

Air conditioning system consists of the compressor, the condenser, a throttle, the evaporator, container with coolant and pipelines. In system coolant (R134a type) which depending on temperature and pressure can be in liquid or gaseous state circulates.

The conditioner compressor through a ridge belt is given to rotation from a bent shaft of the engine. He creates pressure to 30 bars in an installation cooling contour owing to what the coolant representing gas heats up. In the condenser coolant is cooled with the air proceeding outside (the cooling air remains in the external environment). Thereof the warmed coolant is condensed, turning into liquid. Having big pressure, it is passed through a throttle therefore its pressure falls. After that coolant evaporates in a contour, at the same time strongly being cooled. In the evaporator coolant selects heat from the air blown through it. Thereof air is cooled. The cooled air comes to interior of the car. As a result of heating in the evaporator coolant turns into gas and under low pressure comes to the compressor then process of circulation repeats.

Security measures at service of the air conditioner

Air conditioning system has to be served by exclusively prepared technicians trained in safe working methods with use of the appropriate equipment with observance of rules of depressurization, acquainted with methods of collecting and order of storage of automobile coolant.
  • Do not allow contact of coolant with skin;
  • During the work near air conditioning system put on goggles;
  • At hit of coolant on skin or eyes do not pound the struck place. Immediately wash out cold water within not less than 15 minutes. Immediately see a doctor or in medical institution. Self-treatment is not allowed;
  • Coolant is stored in a new cylinder under pressure. You store a cylinder at a temperature not above 50 °C. Take the measures excluding falling of a cylinder about heights or other situations which can lead to its damage;
  • Works should be carried out in well aired room. Coolant quickly evaporates, leads to reduction of access of oxygen and the complicated breath;
  • Gaseous coolant is heavier than air and rather quickly has to gather below, for example, under the car;
  • At combustion of coolant poisonous gas is formed. You store coolant far from open sources of fire. You do not smoke. When using an ardent techeiskatel avoid smoke inhalation;
  • When carrying out welding works near air conditioning system to influence of high temperature or an open flame. The overheat can lead to increase in pressure in system and to ignition;
  • Cleaning of the condenser or evaporator by means of water vapor is not allowed. It is necessary to use only cold water or compressed air.