'Auto Air Conditioning' is in the vehicle. There is a loud noise coming from the engine compartment when the air is on. It can best be described as what one hears when you blow up a balloon, remove the opening from your mouth and hold it only tight enough to slowly let air release. I think it is the diaphragm in the "fast idle actuator". I would like to start by replacing it but so far have been unable to source it. Any additional thoughts? Thx.