While air conditioning was previously considered a luxury and was only used in high-priced vehicles, it is now available as standard equipment. Of course, they can be ordered as special equipment for every vehicle. Comfortable temperatures in the vehicle interior have long since ceased to be a luxury; they also play a key role in the safety of vehicle occupants. When it is hot, the ability to concentrate while driving decreases considerably and the risk of an accident increases considerably. To avoid this, a functioning air conditioning system is an advantage. In order for it to work properly, it should be serviced at regular intervals.
How is an air conditioning system constructed?
Similar to a refrigerator, the main component of an air conditioning system is a refrigerant that is integrated into a cycle. By changing its physical state, it absorbs heat on the one hand and gives it off again at another point. The functions in detail:
An air conditioning compressor first draws in the gaseous refrigerant and compresses it, whereupon it is heated by the high pressure. The heated, gaseous refrigerant is now led to the condenser (cooler) via lines. This is located in the front of the vehicle and is usually equipped with additional fans to allow the refrigerant to cool down quickly. In the condenser, the refrigerant, which is still gaseous, returns to a liquid state due to the cooling, but which is still under high pressure. In the subsequent dryer, any water and foreign matter that may still occur are filtered out of the coolant before it flows further into the expansion valve. After it has passed the narrow valve, the liquid in the evaporator can relax again and thus takes on its gaseous state again.
The heat required for this process must be extracted from the air flowing past the evaporator. The cold air created by the heat exchange is now fed into the interior of the vehicle by the ventilation system in order to cool it down. The cycle starts again when the compressor draws in the gaseous refrigerant again. The cool air is not fed directly into the interior, but has to pass through the interior filter beforehand. Its task is to remove pollutants and pollen from the air and to supply the interior with the cleaned air.
Components such as the compressor, evaporator or expansion valve are checked during regular maintenance. But seals and hoses are not maintenance-free either: they should be checked annually to determine whether there are any leaks. The air conditioning compressor can be divided into different types, with the swash plate compressor being the most frequently used type. It consists of a housing with compressor parts and valves as well as a connection piece for the refrigerant lines. When the air conditioning is switched on, a belt pulley with a magnetic clutch starts the compressor attached to the engine block via a V-belt.
What is used as a refrigerant?
The previously used tetrafluoroethane, short name R134a, had too high a global warming potential and so an EC directive was passed to only use refrigerants with a global warming potential of less than 2011 from 150. This applied to vehicles that were granted type approval for operation in the EU from January 1, 2011. Vehicles with the refrigerant R134a may no longer be registered for the first time since January 1, 2017. But the new refrigerant R1234yf from the US chemical company Honeywell and Dupont, which has been in use since then, is also controversial because the extremely flammable refrigerant can release highly toxic chemicals in the event of an engine fire.
Another alternative is the use of CO2 (carbon dioxide) as a refrigerant in air conditioning systems. The non-flammable, inexpensive gas is about 1.430 times less damaging to the climate than the previously used refrigerant R134a. In addition, it does not form any decomposition products and, thanks to its high cooling capacity, is an ideal refrigerant for this use. Heat pumps can also be operated with CO2, also known as R774 refrigerant. You can also help to save additional energy in winter with cooling and heating concepts.
Many car manufacturers such as Daimler or VW are already using CO2 as a refrigerant in future vehicles. Mercedes-Benz took on a pioneering role in the development of CO2 as a refrigerant. In Europe, the S-Class and E-Class are the world's first series vehicles to be offered with CO2 air conditioning systems. Since a fleet-wide use of the CO2 air conditioning systems could not be complied with by the specific deadline of the EU directive on January 1, 2017, the car manufacturer developed safe solutions for its vehicles in which the flammable refrigerant R1234yf is used. The trigger for the development of the CO2 air conditioning systems at Daimler was a crash test in which the highly corrosive hydrofluoric acid was formed due to a fire in the engine compartment through the escape of the refrigerant R1234yf.
The VW Group is also planning to gradually equip its vehicle fleet with the new refrigerant CO2. The VW subsidiary Audi will be installing CO2017 air conditioning systems in its vehicles as early as 2, presumably first in the luxury A8 sedan. The use of CO2 as a refrigerant was discovered back in 1988, but the development and conviction in favor of the more climate-friendly refrigerant lasted until 2007, when the German OEMs and their suppliers, together with the VDA, agreed to use CO2 in the air conditioning systems of their series vehicles.
What is the difference between air conditioning and automatic air conditioning?
Air conditioning is the manual version of air conditioning in the vehicle. A level is selected in which cooling is to take place. If the temperature is too low, it must be readjusted manually. An automatic air conditioning system, on the other hand, adjusts the temperature of the interior to the desired temperature selected by the driver / front passenger. Sensors ensure that the automatic climate control sets and maintains the temperature. Compared to a manual air conditioning system, an automatic air conditioning system can definitely reduce consumption because it avoids unnecessary performance.
Whether manual air conditioning or automatic air conditioning: The consumption of the vehicle increases when using both variants. This can mainly be explained by the fact that the working resistance of the engine is increased by the air conditioning compressor. An additional consumption of 0,5 to 1,0 liters of fuel per 100 km is quite realistic. A distinction must be made between manual, semi-automatic and fully automatic air conditioning. The fully automatic air conditioning can also score points in the ADAC air conditioning test with the lowest additional consumption.
Experience has shown that in purely electric vehicles, switched on air conditioning systems can reduce the range considerably. The ADAC also tested the loss of range of electric cars when cooling with air conditioning at an outside temperature of 30 ° C and found that a reduction in range of almost 6 to 22 percent can be recorded.
Correct use of the air conditioning system
Of course, predictive parking in the shade is a good way to avoid letting the sun overheat the car. But sometimes that's just not possible. If the interior of the vehicle has become hot despite possible measures such as sun protection blinds or sun protection shutters, it is advisable to open all doors before starting the journey in order to release a large part of the heat from the car. If the air conditioning is now switched on while driving, all windows should remain closed so that the air conditioning does not have to perform unnecessarily. In general, the temperature in the interior should be set so that it is around 5 ° C below the outside temperature and not below 22 ° C on longer journeys so that no colds occur. With recirculation mode, not only are the energy savings particularly great, the pollen filter does not clog as quickly and therefore has to be replaced less often.
Not turning on the air conditioning at all to protect it is not an option! At least once a month, including the winter months, the air conditioning should be switched on for a few minutes. If this is not observed, the lubricant in the piston can no longer be evenly distributed. The components are leaking and the refrigerant can escape. This is not only harmful to the environment, it is also expensive to repair. If the air conditioning is not switched on for a long time - for example in winter - mold and bacteria can multiply on the evaporator. When the system is switched on, these are then distributed with the air in the interior, which can be harmful to the health of the occupants of the vehicle.
A mold infestation in the air conditioning system can inevitably be recognized by the smell: If the air released is stinky or smells foul and musty, this is a sure sign of mold. Since mold only forms in places where it is damp, it can be assumed that condensation has formed on the evaporator due to clogged drain valves or drain lines.
Residual moisture on the evaporator can easily be combated by switching off the air conditioning about 3 minutes before parking. The normal fan should be able to fight the residual moisture. In order to subsequently disinfect the air conditioning system, you can visit a workshop or disinfect yourself. This is quite easy to do even for laypeople. Regularly changing the cabin filter is also important to avoid the development of odors and bacteria. The change is usually made during the inspection; in the air conditioning service it is an integral part of the investigation.
How do I know that the air conditioning is defective?
In addition to the aforementioned bad smell when using the air conditioning system, a reduced cooling capacity is an indication of a defect. It is now important to check the air conditioning system for possible leaks to avoid losing too much refrigerant. However, a reduced cooling capacity does not necessarily indicate a leak; the natural depletion of the refrigerant is normal during the year. If there is not enough refrigerant in the circuit, it can be topped up in the workshop if necessary.
Air conditioning service
In order for the air conditioning in the car to work in the long term, it is important to have regular air conditioning services. All important system components such as compressor, condenser, evaporator or expansion valve as well as seals and hoses are checked here. The air conditioning service should be carried out at least every two years, even if it is not specified in the service booklet. Refilling and replacing the refrigerant are also part of the air conditioning service and may only be carried out by specialists with the appropriate devices. The interior is also examined for odors in the workshop with the air conditioning switched on, so that disinfection can be carried out if necessary. Regular maintenance of the air conditioning system not only protects the environment, but also your wallet in the long term, as it ensures that no expensive components such as compressors or condensers are damaged.
The cost of climate maintenance depends on what services have been performed.
If only a pure visual inspection is due, the costs are between 20 and 40 euros.
Thoroughly cleaning the air conditioning system and topping up the refrigerant can cost between 50 and 150 euros, depending on the workshop. Our tip: Do not only consider the air conditioning service in summer, when the temperatures are already high. Spring is best for this date, when the air conditioning does not yet have to provide high performance.
Article from the green car magazine.
Cover picture: The air conditioning in the car - Copyright antic @ fotolia.com
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