So cool and so fresh...?

The HVAC system does not only increase driving comfort, but safety as well—for a cool head in the summer and fog-free windows in the winter. But as the saying goes, input equals output. Even if most car owners believe that HVAC systems are maintenance-free, the system should be serviced every few years. Let us explain why.

Gaseous at first, then liquid, then gaseous again: the refrigerant in an HVAC system is a real quick-change artist! In the compressor, it starts out in a gaseous state. There it undergoes extreme compression and is heated in the process. In this form, it is fed from the compressor to the condenser at the front of the vehicle, and is cooled by headwind and the fan. As it cools, the refrigerant changes to a liquid state. It now flows through the filter dryer and is cleaned, and any remaining water particles are removed. The evaporator is located in the air duct inside the vehicle. This is where the refrigerant changes its state once again, reverting to a gas. The evaporative cooling produced by this process is directed into the cabin and cools the interior. The refrigerant gas is returned to the compressor from the evaporator—and the cycle starts all over again.

As in life, so it goes in the HVAC system: without a little pressure, nothing would ever get done. The refrigerant circuit requires a pressure range up to almost 18 bar. Although the HVAC system is self-contained, it loses a bit of refrigerant during the year, mostly through the hoses and numerous gaskets. In order to determine the amount of refrigerant left in the system, you must first extract it and then measure the exact quantity. Once extracted, the system is depressurized and can be serviced, for example, by replacing the filter dryer. The 170 L/min vacuum pump of the MAHLE A/C service unit then creates a vacuum throughout the entire refrigerant circuit. The high vacuum removes any remaining moisture from the system. At the same time, this also serves as a leak tightness test: if the vacuum remains constant, the system isn’t leaking! After the testing is completed, the MAHLE A/C service unit automatically refills the system with precisely the specified quantity of refrigerant. The MAHLE E³ technology ensures that no refrigerant is released into the environment. Furthermore, the amount of refrigerant oil that was lost in the extraction process is automatically replaced with fresh refrigerant oil.

An amount of refrigerant oil circulates through the system with the refrigerant. This oil mist keeps hoses and gaskets flexible—an absolute must to ensure a leak-tight system and long-lasting components. If there is too little refrigerant in the system, the gaskets and hoses become brittle and leaky. But the compressor suffers too. Its job is to compress as much refrigerant as is required to achieve the desired temperature in the passenger cabin. If there is less than the minimum required amount of refrigerant, the compressor has to work at full load. Even so, it will not be able to achieve the necessary pressure and therefore the desired temperature in the vehicle. It overheats. The refrigerant oil burns and cokes, which reduces its lubricity. Worse still, metallic abrasions and chips from the compressor may damage the whole system.

An amount of refrigerant oil circulates through the system with the refrigerant. This oil mist keeps hoses and gaskets flexible—an absolute must to ensure a leak-tight system and long-lasting components. If there is too little refrigerant in the system, the gaskets and hoses become brittle and leaky. But the compressor suffers too. Its job is to compress as much refrigerant as is required to achieve the desired temperature in the passenger cabin. If there is less than the minimum required amount of refrigerant, the compressor has to work at full load. Even so, it will not be able to achieve the necessary pressure and therefore the desired temperature in the vehicle. It overheats. The refrigerant oil burns and cokes, which reduces its lubricity. Worse still, metallic abrasions and chips from the compressor may damage the whole system.

It is recommended to install a new cabin air filter as part of an A/C service. Tips for an odor-free zone.

• Functional test and visual inspection prior to maintenance of the HVAC system
• Leakage test and refilling of the refrigerant and refrigerant oil with the MAHLE A/C service units ArcticPRO
• Exchange the cabin air filter with MAHLE/Knecht filter
• Functional test and visual inspection following maintenance of the HVAC system

On a vehicle’s HVAC system, the cabin temperature should be set no more than 8°C lower than the outside temperature. This means: if the outside temperature is 30°C, the HVAC system should be set to no lower than 22°C.

The cabin air filter should be replaced at every vehicle service, or at least every six months. In the spring, to eliminate the impurities accumulated during the cold season. This enables the HVAC system to work more efficiently over the summer and “breathe freely.” In the autumn, to remove the pollen and pollutants that accumulated over the summer. This ensures that full heating performance can be delivered in the cold season, allowing window panes to be cleared quickly. The driver will enjoy the clean air in the vehicle.

An A/C service should be performed every few years. This ensures that there is always enough refrigerant in the system—for long-lasting and reliable functionality of the HVAC system.