I bought a wondow air conditioner off my neighbor and I brought it home and tried it first. It was a couple of months before I needed to use it. It looked and worked like a new one. Its digital by the way. It stayed on all night but the next day it stopped blowing air and just made a humming noise. The reset button on the cord shows green like the outlet is fine. It sounds just like its going to kick in any moment, but then it doesn't. It just keeps humming, even if you turn it off and back on. It worked so good the first night. It was extremely cold, I thought maybe it was something small worth fixing or the outlet.

By the way 18,000. 220. In addition to the humming you can hear liquid going through lines. Also the cool button lights up, but the on button doesn't.

Take it a part and give it a good cleaning, if this does not work then it may be a capacitor on the fan. Both cheep to do. If neither is the case time to junk the unit as it will cost as much to fix as buy a new.