The mechanic will diagnostic the air conditioner and find the problem .Labour removing and insta new cooling coil, aircon drier, expansion valve & clip . After that vacuum to cleaning it can help solve this problem to some extent and gas refill . -Worm Prompt : Ensure that you clean it once in 30,000-50,000 km or once in two years. These days, premium vehicles come with a filter to prevent this issue. Do not forget to change the filter after 10,000-15,000 km.