The air conditioning condenser

The “liquefier” in the vehicle front

In our “Introducing a product” series, we give you the essential information from the experts about different vehicle technologies and equipment in a compact, uncomplicated form. Here, the focus is on the air conditioning condenser. What is its job? And how does it work? Read on to find the answers.

MAHLE Aftermarket has approximately 1,200 different air conditioning condensers for passenger cars, vans, and commercial vehicles in its range. As a customer of MAHLE Aftermarket, you benefit from its extensive expertise in the OEM business and more than 30 years of experience in A/C service.

Bear in mind that the A/C service is a key service component that will become even more important with electric and hybrid vehicles, as their batteries and power electronics need to be cooled. This means that thermal management components are playing an increasingly important role. No longer simply a comfort feature, they are now also responsible for the service life of the other components and the functioning of the electrified powertrain. This means that regular inspection and maintenance are required.

Components in the air conditioning circuit

The air conditioning condenser is one of the five major players in vehicle air conditioning systems. The others are the air conditioning compressor, the evaporator, the filter-drier, and the expansion valve. If you follow the flow of the refrigerant, the air conditioning condenser comes immediately after the air conditioning compressor. Its “workspace” is usually in the vehicle front, behind the radiator grille and in front of the radiator. Behind the components listed above, there’s a fan that switches on automatically if the airstream doesn’t provide enough cooling.


Role and function of the air conditioning condenser


Condensing means that a substance changes from a gaseous to a liquid state. In the air conditioning system, this substance is the refrigerant. The compressor draws it in in a gaseous state and compresses it. As a result, it is heated significantly and then pressed into the top of the air conditioning condenser under high pressure. Its task is now to cool the hot refrigerant via pipes and fins or to discharge heat to the surroundings. This lowers the pressure and causes the refrigerant to liquefy. Due to the cooling, the refrigerant then leaves the condenser at the lower connection in a liquid state.

Symptoms and types of damage


Because of its position at the vehicle front, the air conditioning condenser is permanently exposed to wind, weather, and stone chips. It’s likely to get damaged during the life of a vehicle. Leaks in the air conditioning condenser are one of the most common reasons why the air conditioning system might stop working. However, thermal overload—e.g., because of a defective fan or insufficient heat transfer due to contamination—can also affect the condenser.


A defect in the air conditioning condenser therefore reduces the cooling capacity or even causes the entire air conditioning system to fail. This can also be a gradual process, if corroded or missing fins impair the condenser’s cooling performance. A continuously running condenser/radiator fan may indicate a defect. So, if a customer brings a vehicle with these symptoms to your workshop, it’s advisable to check whether there is enough refrigerant in the cooling circuit, look for leaks, contamination, or damage, and carry out a pressure test on both the high- and low-pressure sides.

Quick check

Symptoms of a defective air conditioning condenser:

  • Poor cooling capacity
  • Failure of the air conditioning system
  • Continuously running condenser/radiator fan

Test steps to eliminate the defect:

  • Check refrigerant charge
  • Check air conditioning condenser for contamination
  • Test for leaks
  • Pressure test on the high- and low-pressure sides


We regularly provide technical tips relating to the powertrain, thermal management, and mechatronics in automobiles.


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