The air taken in enters the heater radiator and heats up there, or to the air conditioner evaporator, where it is cooled, and from where it is already heated or cooled through the air distribution dampers to the deflectors in the cabin.
Deflectors on the instrument panel provide warm air to the front glass, to the wiper blades in their original position. This ensures that the rubber bands of the brushes are warmed up in winter and ice is removed from them.
Hot coolant constantly circulates in the heater core, heating it.
The fresh air passing through the heater core picks up this heat and thus heats up.
The temperature of the air supplied to the passenger compartment is controlled by proportional mixing of hot and cold air.
Thus, the functioning of the heater depends on the air temperature (see illustration 10.0). The air-distributing dampers of the heater are driven by executive electric motors or cable rods. To increase air exchange in the car interior, the fan can operate at four speeds.
10.0 Interior heating and ventilation
1 - heater / air conditioner switch panel
2 - side deflector
3 - windshield air deflectors
4 - central deflectors
5 - deflectors for blowing the rear of the cabin
For this purpose, each stage of rotation of the fan motor has a corresponding additional resistance. If one of the additional resistances fails, the resistance board must be replaced as a set.
If, for example, due to contamination of the outside air, it is necessary to turn off its intake, then the air recirculation mode can be maintained in the passenger compartment, i.e. only the air in the cabin will be used.
Attention! If, as part of the work on the heater, work will also be carried out on electrical equipment, then it is imperative to disconnect the wire terminal from the negative terminal «masses» (-). Even the simple disconnection of a wire or connection terminal is considered work on electrical equipment.
A-class cars with a diesel engine, starting from 3/01, are additionally equipped with an electric heater, which is a heating element located in the heater radiator.
When the air temperature drops below +8°C, the electric heater turns on automatically and heats the air in the passenger compartment to the set temperature, and then turns off.
Air conditioner
The air conditioner works like a refrigerator.
Compressor 7 (see illustration 10.0a) compresses the gaseous, environmentally friendly and CFC-free refrigerant R-134A.
10.0a Air conditioner and how it works
1 - blower fan
2 - evaporator
3 - throttle valve
4 - container with refrigerant
5 - cooling radiator fan
6 - radiator
7 - compressor
a - air flow when the car is moving, cooling radiator
b - hot air
c - uncooled air supplied by the fan
d - cooled air supplied to the passenger compartment
A - high blood pressure (gaseous refrigerant)
B - high pressure (liquid refrigerant)
C - low pressure (liquid refrigerant)
D - low pressure (gaseous refrigerant)
As a result, the refrigerant is heated and it enters the radiator, where it is cooled and liquefied.
Through the throttle valve 3, the refrigerant is fed into the evaporator 2, where the resulting liquid again passes into a gaseous state. In this case, it is strongly cooled, as a result of which the air taken from outside is also cooled. At the same time, the moisture contained in the air is converted into condensate, which is discharged outside.
The intensity of air cooling depends on the set temperature in the passenger compartment, as well as on the speed of rotation of the blower fan.
The air conditioner can work on the principle «Reheat» (reheating) air.
When the ambient air temperature is above +1°C, the air conditioner compressor works, which means that the air conditioner first cools the incoming air and then heats it on the evaporator to the desired temperature.
During cooling, the air is dried, which prevents the windows from fogging up.
On request, A-class cars can be equipped with automatic air conditioning.
Attention! Service and repair of the air conditioner should only be entrusted to a specialized workshop.
Attention! Do not open the air conditioner refrigerant circuit. Skin contact with coolant causes frostbite. If refrigerant comes into contact with the skin, immediately rinse the skin with cold water for at least 15 minutes. The refrigerant is colorless, odorless and heavier than air. If a refrigerant leaks, people near the floor where the vehicle is parked or in rooms below the leak may suffocate.