I have a fairly new Whirlpool 5400 a/c. It worked fine for two seasons, now when the compressor kicks in, the thing vibrates. Nothing too bad if it werent in a bedroom, but it is quite annoying. I tried moving it and placing it on foam. It works for a few minutes then makes noise again. I had a similar problem with another GE a/c. Repair person said it was the compressor. I cant believe these modern air conditioners give out after just a few years of service. I remember when the old Emerson Quiet Kools and Fedders ran trouble free for 20 years or so. Seems efficiency has given way to reliability.