top of page
  • Marco Bonifaccino

Car Air-Conditioning: check and service.

Updated: Apr 26, 2022

Here you will find useful basic information and handy tips relating to air-conditioning systems in vehicles.

Important safety information

The following technical information and practical tips have been compiled by AC diagnosis, source HELLA, in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this blog is intended for use by suitably qualified personnel only.


The air-conditioning system used to be something reserved for luxury cars. Today it is standard equipment in all vehicle classes. But how does it achieve cooling and which components are actually involved? Here you will find not only find answers to these questions, but also tips on the maintenance, troubleshooting, and repair of air-conditioning systems.

In this article, we're going to talk about:

  1. Function: Air-Conditioning cirquit

  2. Useful information: Air-Conditioning service, recharge and check

  3. Troubleshooting: checking the Air-Conditioning system

  4. Workshop tips: car Air-Conditioning repair - removal and installation instructions



Refrigerant and the cooling circuit are required to control the climate inside the vehicle. A blend of cold and hot air makes it possible to create the desired climate conditions ─ irrespective of the conditions outside. This makes the air-conditioning system a key factor in improving safety and driving comfort.

The individual components of the refrigerant circuit are connected by hoses and/or aluminium pipes and thus form a closed system. Refrigerant and refrigerant oil circulate in the system, driven by the compressor.

How the air-conditioning system with expansion valve works

The circuit has two sides:

  • The section between the compressor and the expansion valve is the high-pressure side (yellow/red).

  • The section between the expansion valve and the compressor is the low-pressure side (blue).

The gaseous refrigerant is compressed by the compressor (thereby significantly increasing its temperature) and pressed under high pressure through the condenser. This removes heat from refrigerant - it condenses and changes its state from gas to liquid.

The filter dryer, the next unit, removes contaminants and air from the liquid refrigerant as well as humidity. This ensures system effectiveness and protects the components from damage caused by contaminants.



Alternating check and service

The air-conditioning system is a system requiring maintenance. It should therefore be inspected at regular intervals in order to prevent damage.

The air-conditioning check and air-conditioning service are comparable to a small and large inspection:

QUICK TIPS. Expert recommends: Perform the air-conditioning check every 12 months and the air-conditioning service every 2 years.



Testing the cooling capacity

In addition to test tools and special tools, every garage requires the relevant specialist knowledge, which can be acquired through training. This applies in particular to air-conditioning systems. Due to the different systems, these instructions can be used as guidelines only.