Theory of operation of the Air Conditioning system


The car's air conditioner is a marriage between car heating and the refrigeration fluid circulation. This enables the creation of controlled climate conditions, completely independent of exterior conditions. Therefore this climate system is a true contribution t safety and comfort in driving.

The refrigerant circulation
The individual components of the refrigerant circulation are interconnected by hoses and tubes and make up a closed system, In the system the refrigerant circulates, powered by a compressor. The system is divided into two parts: the part between the compressor and the expansion valve is called the high-pressure side (yellow/red). The part from expansion valve to the compressor is the low-pressure part (blue).


The refrigerant circulation. Click on the picture icon to expand.

In the compressor the gas state refrigerant is compressed and thus seriously heated. Under high pressure it is pressed into the condensor. Here heat is taken from the gas, and the gas condensates into the fluid state.

The dryer, the next station, separates contamination, air bubbles and water from the refrigerant fluid. This way the effectiveness of the system is ensured and components are protected against damage by any contaminations.

Next is the expansion valve. This valve acts like water dam, keeping a steady pressure on one side and a regular flow thru the opening in the valve. The fluid expands when it flows thru the valve under pressure and because of the increase in volume it absorbs energy from the environment. The expansion valve is directly positioned before to the evaporator, the expansion happens inside the evaporator. While the fluid is expanding into gas from again, heat is taken from the environment.

The evaporator is like a small radiator. It cools down to a low temperature and an electrical driven fan circulates air thru the radiator. This heat exchange cools the air that is then entered into the cabin of the car. The radiator has a similar construction as the condenser, having an increased surface by use of small aluminum plates that help the heat exchange.

A typical system looses 70 up to 100 grams of refrigerant every year due to diffusion from the hoses, seals and links. The refrigerant is not only responsible for the cooling but also lubricates the compressor. Its important that there is always enough refrigerant in the system to ensure the lubrication and prevent any damage and wear of the compressor. Humidity is the enemy of the refrigerant system. The dryer does not only serve as filter contaminations but also to absorb water. It can absorb 6 to 12 grams of water from the refrigerant. It needs to be replaced by a (sealed) new one to ensure proper operation whenever the system is serviced.

During a AC system service the system is evacuated, cleaned, and then pressurized at 10 bar using Nitrogen to locate any leaks. Then the system is refilled with the refrigerant taken from it and topped up to the required amount.

Verbot von R12 Kältemittel !!

Nach der FCKW-Halon-Verbotsverordnung dürfen ab dem 30.06.1998
keine Pkw-Klimaanlagen mehr mit dem Kältemittel R 12 befüllt werden

Als Alternative zur Umrüstung auf das Kältemittel 134a, bieten wir Ihnen die kostengünstige Umrüstung auf den bewährten Ersatzstoff R413a  (DROP IN). Ein Erneuern des Kältemittelöles, sowie ein erneuern sämtlicher Dichtungen und diverser Bauteile entfällt,
wodurch Sie viele hundert Mark sparen!

Das Kältemittel R413a ist FCKW-frei und bietet Ihnen die gleiche Kühlleistung wie das Kältemittel R12.


Some pricing:

Kältemittel Ersetzt Menge Preise in EURO
Kältemittel R 134 a   pro 100 g 4,20 €
Kältemittel R 413 a R 12  pro 100 g 6,00 €
Stickstoff   Pauschal 6,00 €
Arbeitszeit nach Aufwand   1 Std. 40,00 €
Verdampferreinigung   Pauschal 25,00 €
Leck-Indikator   1 Füllung 15,00 €

Preise ink. MWST