Tel: 0118 9410551
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Please call 0118 945 1516 to book an MOT or service.
Car Air conditioning

Air conditioning - How does it work?

Air conditioning is designed to provide cool and dehumidified air into the interior of the vehicle. The cooling effect is achieved by blowing air through a cold evaporator unit into the vehicle interior.

When the air conditioning is on the compressor, which the engine drives, engages and starts to compress the refrigerant gas, raising its temperature and pressure. This hot vapour then passes through the condenser, which is a heat exchange unit, its heat is radiated into the air that passes over the condenser fins. This action cools the refrigerant vapour causing it to condense becoming a liquid. The liquid refrigerant now passes through the receiver-dryer that removes any water from the system preventing the build up of corrosive acids and acting to store high-pressure liquid refrigerant in reserve for the evaporator. On leaving the receiver-dryer the clean dry liquid passes into the expansion valve, which meters and atomises the flow of refrigerant, at low pressure into the evaporator.

Here at the evaporator heat is extracted from the air that passes over the tubes and fins. This cools the air, which enters the vehicle interior, and the heat is transferred to the refrigerant, which reverts to a gas, and the cycle is repeated.

Refrigerant gas R134a

Tetrafluoroethane, R-134a, is a haloalkane refrigerant with thermodynamic properties similar to R12 gas (dichlorodifluoromethane), but with less ozone depletion potential. It has the formula CH2FCF3, and a boiling point of -26.3 °C (-15.34 °F) at atmospheric pressure.

Tetrafluoroethane is an inert gas used primarily as a "high-temperature" refrigerant for domestic refrigeration and automobile air conditioners. These devices began using tetrafluoroethane in the early 1990s as a replacement for the more environmentally harmful R12 gas and retrofit kits are available to convert units that were originally R12-equipped.

Health and Safety

Contact with escaping gas from a pressurised system will cause frost bite and the gas is inflammable and explosive when subjected to sudden temperature changes. If you suspect a leak ask us to check it in a controlled environment.


Car Contacts, 12-18 School Road, Tilehurst, Reading, Berks, RG31 5AL.
Tel: 0118 9451516, Fax: 0118 9452830.
Co.No.1378737 in England. Registered Office : 99, London Street, Reading, RG1 4QA
Vat No 314126207
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