What is it with some A/C's? After a while they start making a vibration noise! I bought this Maytag Air Conditioner from Home Depot (probably refurbished!) about 3 months ago & Now when the cold air kicks in it starts making a vibration noise so freakin annoying. At first it lasted about 30 seconds, but now its lasting over 3 minutes! What is vibrating and can I do anything to stop it? I cleaned the filter and when I lightly bang on it the noise stops. Thanks.