For an air conditioning service the garage connects the climate system to a service machine. This extracts the old refrigerant, dehumidifies and evacuates the circuit (vacuum), checks for leaks in the process and then refills the exact specified amount of fresh refrigerant and compressor oil. Often the cabin (pollen) filter is also replaced and the evaporator disinfected to remove odours and germs.
Over the years every air conditioning system loses some refrigerant by design – around 5 to 10 % per year is normal, because the gas diffuses through seals and hoses. If cooling performance drops, the system takes longer to cool down or only blows lukewarm, there is usually too little refrigerant in the system. A musty smell when switching on also points to a service being due.
An air conditioning service is recommended roughly every 2 years, regardless of whether the system still cools. An important distinction is the refrigerant: older vehicles use R134a, newer ones (from about 2017) the more expensive R1234yf. The two are not interchangeable and require different equipment and prices. A well-maintained system also protects the compressor – a compressor failure is considerably more expensive than regular servicing.
As a guideline (no guarantee): an air conditioning service with R134a costs roughly CHF 100–200, with R1234yf about CHF 200–350 because of the expensive refrigerant. An additional cabin filter or disinfection adds around CHF 30–90. If a leak is found during the leak test, the repair must be calculated separately.