General information and safety precautions (Mercedes-Benz G-Class W463)

Note: See also Part Comfort devices.

The air supplied by the ventilation system to the car interior through the filter can be heated or cooled depending on the user's choice. The heater heat exchanger and the air conditioning evaporator are located in the interior, in the housing under the instrument panel. The entire flow of air supplied to the interior is directed for heating or cooling through the same casing. The temperature and speed of the air flow are regulated using the controls located on the control panel.

The heat generated by the engine is transferred by the coolant to the heating system heat exchanger located in the passenger compartment. The air supplied to the passenger compartment is passed through the heat exchanger and is heated by the heat of the coolant flowing inside it. The intensity of the heating is regulated by mixing cold and hot air in a certain ratio by changing the position of the servo-driven mixing flap.

Used air is removed from the passenger compartment through ventilation openings equipped with check valves.

The flow rate of air passed through the heat exchanger is controlled by selecting the speed mode of the heater fan.

If necessary, the supply of outside air to the passenger compartment can be blocked by switching on the recirculation mode (see Section Comfort devices).

Interior air conditioning system

The functional diagram of a typical air conditioning system is shown in the illustration above. Work on the air conditioning system must be performed by a specialized workshop. Never open the working circuit of the air conditioning system - the refrigerant can cause frostbite if it comes into contact with the skin.

With the help of the air conditioning system, the air temperature in the cabin can be lowered below the ambient temperature. Another function of the air conditioning system is to reduce the humidity of the air supplied to the cabin in damp weather: the air is first cooled, then heated again to the set temperature. Air dehumidification allows for the rapid removal of condensation from the windows.

The A/C system consists of a condenser located in front of the cooling system radiator, an evaporator located in a common casing with the heater heat exchanger, a compressor, a receiver/dryer, and refrigeration tubes connecting the above components. A throttle valve is installed at the evaporator inlet, providing the pressure drop necessary for the system to function. The working fluid in the A/C system tract is refrigerant type R134a, which changes its state of aggregation depending on a combination of determining parameters (temperature and pressure).

The fan supplies cabin air to the evaporator, which operates on the principle opposite to that of a radiator, in which heat is taken from the air and transferred to the coolant. When heated, the coolant evaporates and passes into a gaseous state at the outlet of the evaporator.



Compressor the air conditioner is driven by the engine crankshaft via a belt drive and provides excess pressure in the working tract of the system up to 30 atm. As a result of adiabatic compression, the refrigerant, which is in a gaseous state, is heated. Entering capacitor, the refrigerant is cooled by the through flow of outside air and converted into a high-pressure liquid. When passed through throttle the liquid refrigerant pressure is released. The refrigerant then evaporates in the circuit, simultaneously cooling strongly and passing through evaporator, takes heat from the air blown through it. The cooled air is supplied to the car's interior. As a result of heating in the evaporator, the refrigerant turns into a low-pressure gas and again enters the compressor, after which the process is repeated.

Safety precautions when servicing air conditioning system components

Warning! The system is under pressure! Do not attempt to disconnect any pipes related to the air conditioning system without first removing the working fluid from it. Removing fluid from the system is a fairly complex operation that should be performed at a service station. The system contains R134a refrigerant. Make sure that the station has the necessary equipment for this type of refrigerant. Use safety glasses when disconnecting system pipes.

The air conditioning system must be serviced only by trained technical personnel, trained in safe operating practices, using the proper equipment, observing the rules for depressurization, familiar with the methods of collecting and storing automotive refrigerant.

• The currently used refrigerant R134a is much less aggressive than the previously used refrigerant type R12. However, it is very dangerous to health - if it gets into the eyes or comes into contact with the skin, the refrigerant can cause burns. Although the refrigerant R134a is not toxic, its vapors can cause suffocation - do not discharge the system in a closed room under any circumstances. Remember that refrigerant vapors are heavier than air, try not to climb into the inspection pit during the system discharge;
• When refrigerant vapors come into contact with an open flame, a toxic gas is released, which, when mixed with air in a certain proportion, can become explosive. Inhaling refrigerant vapors through a lit cigarette can lead to tragic consequences;
• Do not allow the refrigerant to enter the atmosphere. Unlike R12, the refrigerant R134a does not cause destruction of the ozone layer, but contributes to the development of the greenhouse effect in the atmosphere;
• The A/C system uses sealing elements made of a special material designed to work with a specific type of refrigerant (for 134a - green). In order to prevent the wrong type of refrigerant from accidentally entering the working circuit, special adapter nozzles are used when filling the system;
• The system must be discharged at a Mercedes-Benz authorized service station;
• Before carrying out any work related to heating any vehicle components (welding, soldering, drying after painting), the system should be discharged. The need to discharge the system also arises in the event of servicing its components;
• Always wear safety glasses when servicing A/C system components;
• If refrigerant gets on your skin or in your eyes, do not rub the affected area - immediately rinse it with plenty of cold water, then seek medical attention;
• The refrigerant in a new cylinder is under pressure. Store the cylinder at a temperature not higher than 50°C. Try to avoid the cylinder falling from a height or other situations that may result in damage;
• Maintenance of the air conditioning system components should be carried out in a well-ventilated area - the refrigerant is highly volatile and the accumulation of its vapors can lead to breathing difficulties;
• Cleaning the condenser or evaporator with water vapor is not permitted - use only cold water or compressed air.