I have a Harbor Breeze Lakeside II ceiling fan (five years old) in our bedroom that...
After being on for a couple of hours begins to make an intermittent groaning / humming sound... loud enough to awaken us out of our sleep. It is not a constant sound, but more like a waw-waw-waw-waw sound at low speed. It works perfectly fine other than the noise. And it works great without the groaning / humming sound for a couple of hours. It has a four light fixture attached, three speed, no remote (wall switch and pull chains). Motor? Lubrication? Bearings? Any ideas?

First check and see if something is loose. Blades, screws, light glass.. .

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