How does car air conditioning work and how should you take care of it?

Air conditioning is now a standard feature in almost every car. It's hard to imagine driving without it – not only on hot days but also in winter when it helps remove condensation from windows. It's a system that significantly increases comfort and driving safety, provided it's functioning properly and properly maintained.

Below you'll find a comprehensive overview of how it works, common issues, and the most important maintenance and proper use tips for car air conditioning.

Table of Contents:

1. Construction and operation of air conditioning

2. Symptoms of system malfunction

3. How to maintain your car's air conditioning?

1. Construction and Operation of Air Conditioning

The air conditioning system consists of several key components that work together in a closed circuit. If just one of them isn't working properly, the entire system's efficiency drops dramatically.

Basic components of air conditioning:

1. Compressor
Driven by a belt, the compressor is responsible for circulating the refrigerant in the system. It draws in low-pressure gas, compresses it, and directs it to other parts of the system.

2. Condenser (AC radiator)
This is where the hot gas releases heat to the environment and condenses – changing from a gaseous to a liquid state.

3. Expansion valve (or orifice tube)
Its job is to reduce the pressure of the refrigerant and prepare it for re-evaporation in the evaporator.

4. Evaporator
Located inside the cabin. The low-pressure liquid evaporates, absorbing heat from the air. As a result, cool air flows from the vents.

5. Receiver-drier (filter)
Its role is to trap moisture and contaminants that could damage the compressor or other system components.

Refrigerant – The Heart of the System

Air conditioning couldn't function without the refrigerant that circulates in a closed loop. It's what transfers heat and enables the phase change between gas and liquid.

Currently, three types of refrigerants are used in vehicles:

• R134a (tetrafluoroethane) – Commonly used in vehicles manufactured until 2017. It offers good efficiency but has a high GWP (global warming potential).

• R1234yf (tetrafluoropropene) – A modern gas, mandatory in vehicles sold in the EU after 2017. It has a much lower environmental impact but is significantly more expensive and requires specific service equipment.

• R744 (carbon dioxide, CO₂) – The latest solution used mainly in premium and electric vehicles (e.g., Mercedes-Benz, VW ID.4, Audi e-tron). It's a natural, eco-friendly refrigerant with zero ozone depletion potential and very low GWP = 1. However, it operates at much higher pressures (up to 130 bar), requiring a completely different system design, including a special compressor and evaporator.

Depending on the car model, the system contains between 300 to 1000 grams of refrigerant. Additionally, there's compressor oil in the circuit, which lubricates and protects the compressor from seizing.

2. Symptoms of Faulty Air Conditioning

The most common sign of air conditioning failure is, of course, reduced cooling efficiency. The causes can vary – from refrigerant loss and leaks to compressor failure.

Typical problem symptoms:

• weak or no cooling,

• noise from the vents or compressor,

• unpleasant odor in the cabin,

• weak airflow,

• intermittent system operation.

Causes and Diagnosis

• Low refrigerant level – The gas naturally leaks through micro-leaks (up to 10–15% annually). Its loss results in pressure drop and reduced efficiency.

• Compressor seizure – Often caused by lack of oil or system contamination (e.g., by corrosion, water, or metal particles). It manifests as loud operation or metallic noise.

• Dirty cabin filter – Restricts airflow, causing weak ventilation. Filter replacement is inexpensive and should be done every 10,000–15,000 km.

• Unpleasant odor – Indicates mold and bacteria growth in the evaporator. Requires chemical disinfection or ozone treatment.

• Clogged lines – Can cause intermittent system operation during longer trips.

3. How to Maintain Your Car's Air Conditioning

Proper operation is the most effective way to ensure your air conditioning works quietly and efficiently for a long time. Here are the key principles to remember.

Air Conditioning Maintenance Guidelines:

1. Ventilate the interior before turning on the AC.
   When the car has been sitting in the sun, the cabin temperature can exceed 60°C. Open the doors or windows briefly to let out the hot air – the system will reach effective cooling faster.

2. Run the air conditioning regularly, even in winter.
   Turn it on for a few minutes every few days, even in cold months. This helps distribute oil in the system and prevents compressor seizure.

3. Don't open windows while the AC is running.
   The system works best in a closed cabin – letting in hot air from outside reduces efficiency and puts more strain on the compressor.

4. Check the refrigerant level regularly.
   A 10–20% gas loss can significantly reduce efficiency. Refilling should be done at a workshop with the appropriate service station (for R134a, R1234yf, or R744).

5. Disinfect the system at least once a year.
   Removing bacteria, mold, and fungi from the evaporator protects your health and eliminates unpleasant odors. Effective methods include ozone treatment or ultrasonic cleaning.

6. Replace the cabin filter at least once a year.
   Best done before summer. Activated carbon filters also reduce odors and allergens.

7. Have an annual inspection by a professional.
   A professional check can detect leaks, refrigerant loss, oil level, and compressor condition before a breakdown occurs.

8. Respond to the first signs of trouble.
   Ignoring noise, odors, or weak cooling often leads to expensive compressor replacement. Early intervention is much cheaper.

Summary

Air conditioning is not a luxury but a system that affects driving safety and comfort. To ensure trouble-free operation, it needs regular use and periodic maintenance.
Modern refrigerants like R744 (CO₂) are a step toward ecology but require precise servicing – which is why maintenance should be entrusted to specialists with the right equipment.