Mercedes M-Class W163

since 1997 release

Repair and operation of the car

Systems of ventilation, heating and air conditioning

General information and security measures

See also Part Comfort of the Head Governing bodies and methods of operation.

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.

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 Governing bodies and methods of safe operation).

Air conditioning system of salon

Scheme of a contour of the conditioner of air

1 — the Fan 2 — the Evaporator 3 — the Broad valve 4 — the Tank 5 — the condenser Fan 6 — the Condenser 7 — the Compressor and — External air for cooling of the condenser	b — the Warm air which is taken away outside with — not cooled air going via the fan d — the Cooled air going to salon And — High pressure, gaseous In — High pressure, liquid With — Low pressure, liquid D — Low pressure, gaseous

The function chart of the typical air conditioning system is submitted on an illustration. 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 connecting pipelines.

The air conditioning system consists of the condenser located before a radiator of the cooling system, the evaporator located in the general casing with the heat exchanger of a heater, the compressor, a receiver/dehumidifier, and also the refrigerator tubes connecting the listed above components. On an entrance of the evaporator the gate providing pressure difference necessary for functioning of system is installed. As working liquid in a path of the K/V system the coolant like R134a changing the aggregate state depending on a combination of the defining parameters (temperature and pressure) is used.

The fan provides supply of saloon air to the evaporator functioning by the principle, the return principle of functioning of a radiator, in the carburetor heat is selected from air and transferred to coolant. Being warmed, coolant evaporates and at the exit from the evaporator turns into gaseous state.

The compressor of the conditioner is given to rotation from a bent shaft of the engine by means of the belt drive and provides in a working path of system excessive pressure to 30 atm. As a result of adiabatic compression the coolant which is in gaseous state, heats up. Coming to the condenser coolant is cooled with a through stream of external air and, being condensed, turns into the liquid which is under high pressure. At a transmission through a throttle pressure of liquid coolant is dumped. Further, coolant evaporates in a contour, at the same time strongly being cooled and, passing through the evaporator, selects heat from the air blown through it. The cooled air moves in interior of the car. As a result of heating in the evaporator coolant turns into gas of low pressure and again comes to the compressor then process of circulation repeats.

Security measures at service of components of air conditioning system

The system is under pressure! Do not try to disconnect any tubes concerning the air conditioning system previously without having removed from it working liquid. Removal of liquid from system - rather difficult operation which has to be carried out at the station of service. In system there is a coolant of the R134a type. Make sure that at the station there is necessary for this purpose like coolant an equipment. Use goggles, disconnecting system tubes.

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.

• The R134a coolant which is used now is much less aggressive, than the coolant of the R12 type used earlier. Nevertheless, it is very hazardous to health. Do not allow its hit in eyes or on skin - you can get burn. Though it is also not toxic, its couples can cause suffocation - do not delete it from system, being indoors. Its couple it is heavier than air therefore you are not under the car during its removal from system;
• Do not allow contact of vapors of coolant with naked flame. At its combustion poisonous gas is emitted. The gas mixed with air in a certain proportion can become explosive. Steam inhalation through the lit cigarette can lead to tragic consequences;
• Do not allow hit of coolant in the atmosphere. Unlike R12 coolant like R134a does not cause destruction of an ozone layer, but leads to emergence of greenhouse effect in the atmosphere;
• In system the consolidations made of the special material intended for work with the set coolant type are used (for 134a — green color). Incidentally not to mix various types of coolants, for gas station of a certain type of coolant adapters are used a certain type;
• The discharge of system should be carried out on HUNDRED Mercedes-Benzs;
• Before carrying out any works connected with heating of any knots of the car (welding, the soldering, drying after painting), discharge system. It is also necessary to discharge system before carrying out service any of knots of the air conditioning system;
• During the work near air conditioning system put on goggles;
• At hit of coolant on skin or in 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 differs in a high volatility and the congestion of its vapors is capable to bring to breath difficulty;
• Gaseous coolant is heavier than air and rather quickly has to gather below, for example, under the car;
• Cleaning of the condenser or evaporator by means of water vapor is not allowed, - use only cold water or compressed air.