I had an issue with air condition on my 2.0ltr 59 plate Audi A5. The garage i took car for repair diagnosed air condition unit would need to be replaced. I was told that new air con unit from Audi parts dealership would cost me in the region of £900 , however he could fit new air con unit that was not from Audi dealer for £400. The job was completed using non parts and everything worked again as normal. After driving car for a day or two i noticed a strange intermittent rattle/noise coming from air con unit so I took car straight back to the garage to find out what this noise can be.The car was returned to me the next day with the owner of the garage explaining that the air condition bottle needed to be refilled after fitting and that this will stop the strange intermittent noise i was hearing. I was also advised that it was common practice to leave air con on permanently in the vehicle..?? I questioned this as air con runs on fuel and was told that for the amount of fuel used it would still be in my best interest to leave air con on permanently. I was not convinced about leaving air con on permanently but noise was gone everything worked again as it should and off i went...(with air con off) I didn't even get car home but intermittent rattle/noise was back again, I wondered why I was given the speech about leaving air con on permanently in the first place so I turned it on and sure enough the annoying intermittent noise coming from air con didnt go away but it did however ease slightly and was maybe not just as frequent as before . Has anyone ever heard of this type of issue with air con... Can it be repaired..?