never ever use WD 40 for an electric fan motor. I have used a mix of Liquid wrench and Electric motor oil to break loose a motor but after it was broke loose I used Electric Motor Oil you can pick it up pretty easy. Comes in a small bottle with a looooooong thin snout that you put into the oil hole of the fan motor and fill it. But what you got is pretty normal these new electric motors will usually only last a year. You will find the same thing on lots of window units as well now. But if you did not have any oil holes in the fan motor then the only thing you can do is do what you did and replace the fan motor. You can also get new ones from granger when the warrenty is gone.