There’s an air conditioning condenser in every A/C system, whether in a vehicle with a combustion engine, a hybrid, or an electric car. In most cars, it’s located in the engine compartment in the front section of the vehicle. Its task: to liquify the hot, highly pressurized refrigerant that has been compressed by the compressor, either with the help of cooling ambient air or with the support of a powerful fan.

The A/C condenser is a heat exchanger that’s basically similar in design to an engine radiator. However, it must withstand higher internal pressures of more than 20 bar, which are typical in air conditioning systems. In passenger cars, parallel flow condensers are generally used.

The A/C condenser is assisted by the A/C condenser fan, which sits either in front of or behind it and is available as an add-on or combination fan.

Besides a wide selection of A/C condensers, MAHLE offers finished modules to simplify installation. These are ready-made units comprising a flat-tube condenser and a collection/expansion tank with integrated filter-drier. The MAHLE range includes around 1,200 different A/C condensers and more than 370 fans for cars, vans, and commercial vehicles. When you buy MAHLE Aftermarket products, you benefit from extensive expertise in the OEM business, many years of experience in the development and production of components for vehicles, and more than 30 years of experience in the air conditioning service segment. And that’s not forgetting access to workshop equipment, diagnostics, and comprehensive services relating to air conditioning and cooling. You’ll only get all this from MAHLE.

Purpose and function

After the air conditioning compressor, the A/C condenser is the next component on the high-pressure side in the air conditioning circuit. The compressor compresses the refrigerant, which heats up. The hot refrigerant gas then flows into the condenser installed upstream of the radiator. As it passes through the condenser, the gas gives off heat to the ambient air via the condenser’s pipework and fins. The refrigerant condenses as it cools and changes its state from gas to liquid. The condenser can’t bring about this transition on its own, which is why the condenser fan is there to provide sufficient cooling in all operating conditions. Its task is to support the cooling process and to keep the temperature as constant as possible. Once cooled, the refrigerant exits the A/C condenser as a liquid.

Refrigerant circuit with expansion valve

  1. A/C condenser fan
  2. A/C condenser
  3. A/C compressor
  4. Expansion valve
  5. Cabin fan
  6. Evaporator
  7. Filter-drier

The air conditioning circuit is divided into two sides: the high-pressure side (red/yellow) between the air conditioning compressor and the expansion valve, and the low-pressure side (blue) between the expansion valve and the air conditioning compressor.

More drives, more cooling

A reliably functioning air conditioning system is vital for hybrid and electric vehicles, because it’s also needed to cool the battery and the power electronics. Failure in these vehicles may bring them to a standstill or damage components.

Refrigerant-based circuit (or direct battery cooling) in an electric vehicle

Coolant- and refrigerant-based circuit (or indirect battery cooling) in an electric vehicle

Most common causes of failure

A defective A/C condenser will reduce cooling performance or even lead to the failure of the entire air conditioning system. A condenser fan that’s always running is also often an indication of a defect. If you have any suspicions, check the system for leaks, contamination, and damage. A/C condenser fans can fail due to electrical or mechanical faults. As result, the refrigerant doesn’t liquify sufficiently, causing the performance of the air conditioning system to drop off.

Damaged A/C condenser with deformed cooling fins

A defective A/C condenser may exhibit the following symptoms:

  • Poor cooling performance
  • Failure of the air conditioning system
  • Continuously running A/C condenser fan

Most common causes of failure in A/C condensers and fans:

  • Leaks in and on the A/C condenser due to stone chips, corrosion, defective O-rings
  • Defect due to thermal overload (e.g., if the fan fails)
  • Defect due to contaminants in the refrigerant circuit (sealant clogging the pipes in the condenser)
  • Short circuit or overload of the fan
  • Mechanical deformation due to a collision, for example

Preventing damage

Careful, regular maintenance (in line with manufacturer specifications) is key to a long-lasting air conditioning system. That’s why you should always look at the entire air conditioning system in a customer’s vehicle and check for contamination and leaks in order to spot defects early. If your customer complains about poor cooling performance, you definitely need to do a pressure test on the high- and low-pressure sides. When working on the (opened) refrigerant circuit, make sure you maintain absolute cleanliness so that no dirt particles enter the system.

Tip for your customers: It’s a good idea to wash vehicles regularly, especially in winter, to remove salt and dirt deposits. This helps to prevent corrosion.

Air conditioning and cooling: MAHLE gives you the edge!

You’ll only get all this from MAHLE: a complete range of parts, workshop equipment, diagnostics, and services for engine cooling and air conditioning. MAHLE is THE strong partner for you when it comes to air conditioning and cooling—find out why here.


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