We just recently replaced our fan motor in our outside unit as it had stopped working(we had to keep re-greasing it in order for it to work and to stop it from making a loud squaking noise). We bought a new fan motor and replaced it yesterday. The fan works great but now we hear this loud humming sound. I know that most Air Conditioners make some kind of noise, but we have never heard this before. I don't know if it is just because of the new fan motor working better then our old one that now we have the humming noise or if something else is going on. I do know that the noise is annoying and very loud(our outside unit is located on the outside of the kitchen wall and it can be heard in the kitchen, bathroom, and our sons bedroom). The noise is like a loud humming sound and you here it only when the air is running. It goes away when it kicks off. The fan is working great though and the house is cool...I just have no idea what the noise could be from....any suggestions? I'm driving my husband batty about it so any help would be appreciated.