Hello I own an A3 2008 plate, my car is smooth as anything to drive but when I drive it for the first time in day 24/36 hours it makes a 4/5 second noise of what I can only describe as a fan dying out.

I have recently had had issues with the air con as it completely stoped working and had the radiator replaced which I was told would sort the issue however after 3 weeks of the car running fine the noise happened today and the air con took 2/3 minutes to kick in.

What part do I need to fix this? Is it an alternator issue or water pump? the car starts up fine.