We recommend an aircon service and regas every two years to keep your aircon system working properly. Your car air conditioning system loses up to 15% of its refrigerant every year. A poorly performing car air conditioning system can cause a build-up of fungus, bacteria and other microbes growing inside the evaporator core, causing a smell, sometimes an allergic reaction and can lead to legionnaires disease. A poor air con system can increase your fuel costs, as the air conditioning pump needs to work harder.