I have a 2000 VW bug. When I start the car in the morning or after work (any time it has been sitting for a while) and the air conditioning is on there is a high pitched humming noise. When I turn the air off it stops. Once the car had been running for a few minutes I can turn the air on with no noise. It has been doing this for a while now. Not sure what the problem is or if it is something that I need to get fixed? It is an older car and I am not too keen on spending a ton of money to fix it if the car still runs fine.